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Phytochemistry - Current Research Articles



Current research articles: Phytochemistry

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Phytochemistry - published by Elsevier

Phytochemistry is the international journal of pure and applied plant chemistry, plant biochemistry and molecular biology.




Current articles of the journal:



A novel form of ficin from Ficus carica latex: Purification and characterization

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Danielle Baeyens-Volant, André Matagne, Rachida El Mahyaoui, Ruddy Wattiez, Mohamed Azarkan

A novel ficin form, named ficin E, was purified from fig tree latex by a combination of cation-exchange chromatography on SP-Sepharose Fast Flow, Thiopropyl Sepharose 4B and fplc-gel filtration chromatography. The new ficin appeared not to be sensitive to thiol derivatization by a polyethylene glycol derivative, allowing its purification. The protease is homogeneous according to PAGE, SDS–PAGE, mass spectrometry, N-terminal micro-sequencing analyses and E-64 active site titration. N-terminal sequencing of the first ten residues has shown high identity with the other known ficin (iso)forms. The molecular weight was found to be (24,294±10)Da by mass spectrometry, a lower value than the apparent molecular weight observed on SDS–PAGE, around 27kDa. Far-UV CD data revealed a secondary structure content of 22% ?-helix and 26% ?-sheet. The protein is not glycosylated as shown by carbohydrate analysis. pH and temperature measurements indicated maxima activity at pH 6.0 and 50°C, respectively. Preliminary pH stability analyses have shown that the protease conserved its compact structure in slightly acidic, neutral and alkaline media but at acidic pH (<3), the formation of some relaxed or molten state was evidenced by 8-anilino-1-naphtalenesulfonic acid binding characteristics. Comparison with the known ficins A, B, C, D1 and D2 (iso)forms revealed that ficin E showed activity profile that looked like ficin A against two chromogenic substrates while it resembled ficins D1 and D2 against three fluorogenic substrates. Enzymatic activity of ficin E was not affected by Mg2+, Ca2+ and Mn2+ at a concentration up to 10mM. However, the activity was completely suppressed by Zn2+ at a concentration of 1mM. Inhibitory activity measurements clearly identified the enzyme as a cysteine protease, being unaffected by synthetic (Pefabloc SC, benzamidine) and by natural proteinaceous (aprotinin) serine proteases inhibitors, by aspartic proteases inhibitors (pepstatin A) and by metallo-proteases inhibitors (EDTA, EGTA). Surprisingly, it was well affected by the metallo-protease inhibitor o-phenanthroline. The enzymatic activity was however completely blocked by cysteine proteases inhibitors (E-64, iodoacetamide), by thiol-blocking compounds (HgCl2) and by cysteine/serine proteases inhibitors (TLCK and TPCK). This is a novel ficin form according to peptide mass fingerprint analysis, specific amidase activity, SDS–PAGE and PAGE electrophoretic mobility, N-terminal sequencing and unproneness to thiol pegylation.

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Posted on 1 September 2015 | 6:00 am


Changes in gene transcription and taxane production in elicited cell cultures of Taxus×media and Taxus globosa

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Karla Ramirez-Estrada, Lidia Osuna, Elisabeth Moyano, Mercedes Bonfill, Nadia Tapia, Rosa M. Cusido, Javier Palazon

The response of two Taxus cell systems to the action of cyclodextrin (CD) and coronatine (CORO), supplied to the culture medium either separately or together, was studied. Two-stage Taxus globosa and Taxus media cell cultures were established and the elicitors were added at the beginning of the second stage. Growth, taxane production, and the expression of known taxol biosynthetic genes, including the recently characterized CoA ligase gene, were studied. Although CORO reduced the growth capacity of both cell lines, CD apparently counteracted this negative effect. Taxane production was significantly enhanced by the simultaneous addition of CD and CORO to the medium. The total taxane production in the T. media cell line was more than double that of T. globosa, but in the latter more than 90% of the taxanes produced were excreted to the medium. Individual taxane patterns also differed: at the height of production, the main taxanes in T. globosa cultures were cephalomannine and 10-deacetyltaxol, and in T. media, taxol and baccatin III. The low transcript levels of taxane biosynthetic genes found in T. globosa cells mirrored the lower taxane production in these cultures, while a high expression was strongly correlated with a high taxane production in T. media.

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Posted on 1 September 2015 | 6:00 am


Antimicrobial dihydrobenzofurans and xanthenes from a foliar endophyte of Pinus strobus

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Susan N. Richardson, Tienabe K. Nsiama, Allison K. Walker, David R. McMullin, J. David Miller

Foliar fungal endophytes of Pinus strobus (eastern white pine) were collected from different sites across south-eastern New Brunswick, Canada and screened for the production of bioactive metabolites. From one site, two fungal isolates representing a formerly unknown genus and species within the family Massarinaceae (Pleosporales, Dothideomycetes, Ascomycota) were resolved by phylogenetic analysis. These isolates produced crude organic extracts that were active against Microbotryum violaceum and Saccharomyces cerevisiae. From these strains, DAOM 242779 and 242780, four dihydrobenzofurans (14) and two xanthenes (56) were characterized. Structures were elucidated by HRMS, interpretation of NMR spectra and other spectroscopic techniques. All isolated metabolites displayed antimicrobial activity against the biotrophic fungal pathogen M. violaceum and Bacillus subtilis.

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Posted on 1 September 2015 | 6:00 am


Co-expression of vacuolar Na+/H+ antiporter and H+-pyrophosphatase with an IRES-mediated dicistronic vector improves salinity tolerance and enhances potassium biofortification of tomato

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Sandra Gouiaa, Habib Khoudi

Potassium (K) deficiency is a worldwide problem. Thus, the K biofortification of crops is needed to enhance human nutrition. Tomato represents an ideal candidate for such biofortification programs thanks to its widespread distribution and its easy growth on a commercial scale. However, although tomato is moderately tolerant to abiotic stresses, the crop losses due to salinity can be severe. In this study, we generated transgenic tomato plants over-expressing a Na+–K+/H+ exchanger gene (TNHXS1), singly or with H+-pyrophosphatase (H+-PPiase) gene using a bicistronic construct. Transgenic tomato lines co-expressing both genes (LNV) significantly showed higher salinity tolerance than the wild-type (WT) plans or those expressing the TNHXS1 gene alone (LN). Indeed, under salt stress conditions, double transgenic plants produced higher biomass and retained more chlorophyll and catalase (CAT) activity. In addition, they showed earlier flowering and produced more fruits. To address K deficiencies in humans, an increase of 50% in K content of vegetable products was proposed. In this study, ion content analysis revealed that, under salt stress, fruits from double transgenic plants accumulated 5times more potassium and 9times less sodium than WT counterparts. Interestingly, the ionomic analysis of tomato fruits also revealed that LNV had a distinct profile compared to WT and to LN plants. Indeed, LNV fruits accumulated less Fe2+, Ca2+, Mg2+ and Zn2+, but more Mn2+. This study demonstrates the effectiveness of bicistronic constructs as an important tool for the enhancement of biofortification and salt stress tolerance in crops.

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Posted on 1 September 2015 | 6:00 am


Lipid analysis of developing Camelina sativa seeds and cultured embryos

Publication date: October 2015
Source:Phytochemistry, Volume 118

Author(s): Mike Pollard, Tina M. Martin, Yair Shachar-Hill

Camelina sativa is a cultivated oilseed rich in triacylglycerols containing oleic, linoleic, ?-linolenic and eicosenoic acids. As it holds promise as a model species, its lipid synthesis was characterized in vivo and in culture. Lipid accumulates at a maximum rate of about 26?g/day/seed (11.5mglipid/day/g fresh seed weight), a rate comparable with other oilseeds. Noteworthy is a late stage surge in ?-linolenic acid accumulation. Small amounts of unusual epoxy and hydroxy fatty acids are also present in the triacylglycerols. These include 15,16-epoxy- and 15-hydroxy-octadecadienoic acids and homologous series of ?7-hydroxy-alk-?9-enoic and ?9/10-hydroxy-alkanoic acids. Mid-maturation embryos cultured in vitro have growth and lipid deposition rates and fatty acid compositions that closely match that of seeds, but extended culture periods allow these rates to rise and surpass those observed in planta. Optimized thin layer chromatography systems for characterization of labeled products from acetate or glycerol labeling are described. Glycerol label is only found in acylglycerols, largely as the intact glyceryl backbone, but acetate can label acyl groups and sterols, the latter to a much higher relative specific activity. This presumably occurs because mevalonic acid precursor is derived from the non-plastid pool of acetyl-CoA that is also the source for malonyl-CoA to drive FAE1-dependent chain elongation. Particular attention has been paid to the separation of sterols and diacylglycerols, and to hydrogenation of triacylglycerols to simplify their analysis. These improved methods will allow more accurate analyses of the fluxes of lipid metabolism in cultured plant embryos.

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Posted on 1 September 2015 | 6:00 am


Purification, sequencing and characterization of phospholipase D from Indian mustard seeds

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Hafeeza Khatoon, Johanna Mansfeld, Angelika Schierhorn, Renate Ulbrich-Hofmann

Phospholipase D (PLD; E.C. 3.1.4.4) is widespread in plants where it fulfills diverse functions in growth and in the response to stresses. The enzyme occurs in multiple forms that differ in their biochemical properties. In the present paper PLD from medicinally relevant Indian mustard seeds was purified by Ca2+-mediated hydrophobic interaction and anion exchange chromatography to electrophoretic homogeneity. Based on mass-spectrometric sequence analysis of tryptic protein fragments, oligonucleotide primers for cloning genomic DNA fragments that encoded the enzyme were designed and used to derive the complete amino acid sequence of this PLD. The sequence data, as well as the molecular properties (molecular mass of 92.0kDa, pI 5.39, maximum activity at pH 5.5–6.0 and Ca2+ ion concentrations ?60mM), allowed the assignment of this enzyme to the class of ?-type PLDs. The apparent kinetic parameters Vmax and Km , determined for the hydrolysis of phosphatidylcholine (PC) in an aqueous mixed-micellar system were 356±15?molmin?1 mg?1 and 1.84±0.17mM, respectively. Phosphate analogs such as NaAlF4 and Na3VO4 displayed strong inhibition of the enzyme. Phosphatidylinositol 4,5-bisphosphate had a strong activating effect at 2–10mM CaCl2. PLD was inactivated at temperatures >45°C. The enzyme exhibited the highest activity toward PC followed by phosphatidylethanolamine and phosphatidylglycerol. PCs with short-chain fatty acids were better substrates than PCs with long fatty acid chains. Lyso-PC was not accepted as substrate.

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Phospholipase D from Indian mustard seeds was purified to homogeneity. Amino acid sequence data and enzymological properties suggest its assignment to ?-type phospholipases D





Posted on 1 September 2015 | 6:00 am


Discovery of small molecule inhibitors of xyloglucan endotransglucosylase (XET) activity by high-throughput screening

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Dimitra Chormova, Lenka Franková, Andrew Defries, Sean R. Cutler, Stephen C. Fry

Small molecules (xenobiotics) that inhibit cell-wall-localised enzymes are valuable for elucidating the enzymes’ biological roles. We applied a high-throughput fluorescent dot-blot screen to search for inhibitors of Petroselinum xyloglucan endotransglucosylase (XET) activity in vitro. Of 4216 xenobiotics tested, with cellulose-bound xyloglucan as donor-substrate, 18 inhibited XET activity and 18 promoted it (especially anthraquinones and flavonoids). No compounds promoted XET in quantitative assays with (cellulose-free) soluble xyloglucan as substrate, suggesting that promotion was dependent on enzyme–cellulose interactions. With cellulose-free xyloglucan as substrate, we found 22 XET-inhibitors – especially compounds that generate singlet oxygen (1O2) e.g., riboflavin (IC50 29?M), retinoic acid, eosin (IC50 27?M) and erythrosin (IC50 36?M). The riboflavin effect was light-dependent, supporting 1O2 involvement. Other inhibitors included tannins, sulphydryl reagents and triphenylmethanes. Some inhibitors (vulpinic acid and brilliant blue G) were relatively specific to XET, affecting only two or three, respectively, of nine other wall-enzyme activities tested; others [e.g. (?)-epigallocatechin gallate and riboflavin] were non-specific. In vivo, out of eight XET-inhibitors bioassayed, erythrosin (1?M) inhibited cell expansion in Rosa and Zea cell-suspension cultures, and 40?M mycophenolic acid and (?)-epigallocatechin gallate inhibited Zea culture growth. Our work showcases a general high-throughput strategy for discovering wall-enzyme inhibitors, some being plant growth inhibitors potentially valuable as physiological tools or herbicide leads.

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Xenobiotics that inhibit the cell-wall-remodelling enzyme activity, xyloglucan endotransglucosylase (XET), would be a valuable tool in ‘chemical genetics’ for elucidating its biological roles. By screening 4216 small molecules in a dot-blot assay on paper-immobilised xyloglucan, we discovered 45 compounds that inhibited or promoted XET activity. The most effective inhibitors were singlet oxygen generators.





Posted on 1 September 2015 | 6:00 am


Applicability of ISSR and DAMD markers for phyto-molecular characterization and association with some important biochemical traits of Dendrobium nobile, an endangered medicinal orchid

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Paromik Bhattacharyya, Suman Kumaria, Pramod Tandon

Dendrobium nobile is an important medicinal orchid having profound importance in traditional herbal drug preparations and pharmacopeias worldwide. Due to various anthropogenic pressures the natural populations of this important orchid species are presently facing threats of extinction. In the present study, genetic and chemical diversity existing amongst 6 natural populations of D. nobile were assessed using molecular markers, and the influence of genetic factors on its phytochemical activity especially antioxidant potential was determined. Molecular fingerprinting of the orchid taxa was performed using ISSR and DAMD markers along with the estimation of total phenolics, flavonoids and alkaloid contents. Antioxidant activity was also measured using DPPH and FRAP assays which cumulatively revealed a significant level of variability across the sampled populations. The representatives from Sikkim in Northeast India revealed higher phytochemical activity whereas those from Mizoram showed lesser activity. Analysis of molecular variance (AMOVA) revealed that variation amongst the populations was significantly higher than within the populations. The data generated by UPGMA and Bayesian analytical models were compared in order to estimate the genetic relationships amongst the D. nobile germplasm sampled from different geographical areas of Northeast India. Interestingly, identical grouping patterns were exhibited by both the approaches. The results of the present study detected a high degree of existing genetic and phytochemical variation amongst the populations in relation to bioclimatic and geographic locations of populations. Our results strongly establish that the cumulative marker approach could be the best suited for assessing the genetic relationships with high accuracy amongst distinct D. nobile accessions.

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Posted on 1 September 2015 | 6:00 am


Oxylipins in the spikemoss Selaginella martensii: Detection of divinyl ethers, 12-oxophytodienoic acid and related cyclopentenones

Publication date: October 2015
Source:Phytochemistry, Volume 118

Author(s): Anna V. Ogorodnikova, Fakhima K. Mukhitova, Alexander N. Grechkin

Green tissues of spikemoss Selaginella martensii Spring possessed the complex oxylipins patterns. Major oxylipins were the products of linoleic and ?-linolenic acids metabolism via the sequential action of 13-lipoxygenase and divinyl ether synthase (DES) or allene oxide synthase (AOS). AOS products were represented by 12-oxophytodienoic acid (12-oxo-PDA) isomers. Exceptionally, S. martensii possesses high level of 12-oxo-9(13),15-PDA, which is very uncommon in flowering plants. Separate divinyl ethers were purified after micro-preparative incubations of linoleic or ?-linolenic acids with homogenate of S. martensii aerial parts. The NMR data allowed us to identify all geometric isomers of divinyl ethers. Linoleic acid was converted to divinyl ethers etheroleic acid, (11Z)-etheroleic acid and a minority of (?5Z)-etheroleic acid. With ?-linolenate precursor, the specificity of divinyl ether biosynthesis was distinct. Etherolenic and (?5Z)-etherolenic acids were the prevailing products while (11Z)-etherolenic acid was a minor one. Divinyl ethers are detected first time in non-flowering land plant. These are the first observations of fatty acid metabolism through the lipoxygenase pathway in spikemosses (Lycopodiophyta).

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Posted on 1 September 2015 | 6:00 am


Diacylglyceryltrimethylhomoserine content and gene expression changes triggered by phosphate deprivation in the mycelium of the basidiomycete Flammulina velutipes

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Svetlana V. Senik, Liliya G. Maloshenok, Ekaterina R. Kotlova, Alexey L. Shavarda, Konstantin V. Moiseenko, Sergey A. Bruskin, Olga V. Koroleva, Nadezhda V. Psurtseva

Diacylglyceryltrimethylhomoserines (DGTS) are betaine-type lipids that are phosphate-free analogs of phosphatidylcholines (PC). DGTS are abundant in some bacteria, algae, primitive vascular plants and fungi. In this study, we report inorganic phosphate (Pi) deficiency-induced DGTS synthesis in the basidial fungus Flammulina velutipes (Curt.: Fr.) Sing. We present results of an expression analysis of the BTA1 gene that codes for betaine lipid synthase and two genes of PC biosynthesis (CHO2 and CPT1) during phosphate starvation of F. velutipes culture. We demonstrate that FvBTA1 gene has increased transcript abundance under phosphate starvation. Despite depletion in PC, both CHO2 and CPT1 were determined to have increased expression. We also describe the deduced amino acid sequence and genomic structure of the BTA1 gene in F. velutipes. Phylogenetic relationships between putative orthologs of BTA1 proteins of basidiomycete fungi are discussed.

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Posted on 1 September 2015 | 6:00 am


Sequential oxidation of Jasmonoyl-Phenylalanine and Jasmonoyl-Isoleucine by multiple cytochrome P450 of the CYP94 family through newly identified aldehyde intermediates

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Emilie Widemann, Bernard Grausem, Hugues Renault, Emmanuelle Pineau, Clément Heinrich, Raphaël Lugan, Pascaline Ullmann, Laurence Miesch, Yann Aubert, Michel Miesch, Thierry Heitz, Franck Pinot

The role and fate of Jasmonoyl-Phenylalanine (JA-Phe), an understudied conjugate in the jasmonate pathway remain to be unraveled. We addressed here the possibility of JA-Phe oxidative turnover by cytochrome P450s of the CYP94 family. Leaf wounding or fungal infection in Arabidopsis resulted in accumulation of JA-Phe, 12-hydroxyl (12OH-JA-Phe) and 12-carboxyl (12COOH-JA-Phe) derivatives, with patterns differing from those previously described for Jasmonoyl-Isoleucine. In vitro, yeast-expressed cytochromes P450 CYP94B1, CYP94B3 and CYP94C1 differentially oxidized JA-Phe to 12-hydroxyl, 12-aldehyde and 12-carboxyl derivatives. Furthermore, a new aldehyde jasmonate, 12CHO-JA-Ile was detected in wounded plants. Metabolic analysis of CYP94B3 and CYP94C1 loss- and gain-of-function plant lines showed that 12OH-JA-Phe was drastically reduced in cyp94b3 but not affected in cyp94c1, while single or double mutants lacking CYP94C1 accumulated less 12COOH-JA-Phe than WT plants. This, along with overexpressing lines, demonstrates that hydroxylation by CYP94B3 and carboxylation by CYP94C1 accounts for JA-Phe turnover in planta. Evolutionary study of the CYP94 family in the plant kingdom suggests conserved roles of its members in JA conjugate homeostasis and possibly in adaptative functions. Our work extends the range and complexity of JA-amino acid oxidation by multifunctional CYP94 enzymes in response to environmental cues.

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Posted on 1 September 2015 | 6:00 am


Repellency of ?-pinene against the house fly, Musca domestica

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Aaron T. Haselton, Angela Acevedo, Jacob Kuruvilla, Eric Werner, Jaydon Kiernan, Preeti Dhar

Musca domestica L. is a non-biting nuisance fly that is capable of transmitting a large variety of pathogens to humans and non-human animals. Natural compounds and their derivatives, which are often less toxic than entirely synthetic compounds, may be used as repellents against M. domestica as part of comprehensive pest control and disease mitigation programs. This work investigates the repellent properties of the natural compound ?-pinene against M. domestica. Adult house flies of both sexes avoided the volatile plant-derived terpenes (1S)-(?)-?-pinene 1 and (1R)-(+)-?-pinene 2 in constant air flow laboratory conditions, with 1 exhibiting a stronger repellent effect. House flies also avoided tarsal contact with filter paper saturated with 1. Furthermore, both 1 and 2 are electrophysiologically active on in situ female house fly antennal preparations. These findings demonstrate that ?-pinene exhibits natural baseline repellency against the house fly, elicits a specific physiological response in this fly, and that functional or structural modification of 1 in particular may yield novel fly repellents with desirable properties.

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Posted on 1 September 2015 | 6:00 am


Enhanced tocopherol levels during early germination events in Chamaerops humilis var. humilis seeds

Publication date: October 2015
Source:Phytochemistry, Volume 118

Author(s): Laura Siles, Leonor Alegre, Verónica Tijero, Sergi Munné-Bosch

Most angiosperms accumulate vitamin E in the form of tocopherols in seeds, exerting a protective antioxidant role. However, several palm trees principally accumulate tocotrienols, rather than tocopherols, in seeds, as it occurs in other monocots. To unravel the protective role of either tocopherols or tocotrienols against lipid peroxidation during seed germination in Chamaerops humilis var. humilis; seed viability, natural and induced germination capacity, seed water content, malondialdehyde levels (as an indicator of the extent of lipid peroxidation) and vitamin E levels (including both tocopherols and tocotrienols) were examined at various germination phases in a simulated, natural seed bank. At the very early stages of germination (operculum removal), malondialdehyde levels increased 2.8-fold, to decrease later up to 74%, thus indicating a transient lipid peroxidation at early stages of germination. Tocopherol levels were absent in quiescent seeds and did not increase during operculum removal, but increased later presumably dampening malondialdehyde accumulation. Thereafter, tocopherols continued increasing, while lipid peroxidation levels decreased. By contrast, tocotrienols levels remained constant or even decreased as germination progressed, showing no correlation with lipid peroxidation levels. We hypothesize that despite their high tocotrienol content, seeds synthesize tocopherols during germination to protect lipids from peroxidation events.

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Posted on 1 September 2015 | 6:00 am


Characterisation of the willow phenylalanine ammonia-lyase (PAL) gene family reveals expression differences compared with poplar

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Femke de Jong, Steven J. Hanley, Michael H. Beale, Angela Karp

Willow is an important biomass crop for the bioenergy industry, and therefore optimal growth with minimal effects of biotic and abiotic stress is essential. The phenylpropanoid pathway is responsible for the biosynthesis of not only lignin but also of flavonoids, condensed tannins, benzenoids and phenolic glycosides which all have a role in protecting the plant against biotic and abiotic stress. All products of the phenylpropanoid pathway are important for the healthy growth of short rotation cropping species such as willow. However, the phenylpropanoid pathway in willow remains largely uncharacterised. In the current study we identified and characterised five willow phenylalanine ammonia-lyase (PAL) genes, which encode enzymes that catalyse the deamination of l-phenylalanine to form trans-cinnamic acid, the entry point into the phenylpropanoid pathway. Willow PAL1, PAL2, PAL3 and PAL4 genes were orthologous to the poplar genes. However no orthologue of PAL5 appears to be present in willow. Moreover, two tandemly repeated PAL2 orthologues were identified in a single contig. Willow PALs show similar sub-cellular localisation to the poplar genes. However, the enzyme kinetics and gene expression of the willow PAL genes differed slightly, with willow PAL2 being more widely expressed than its poplar orthologues implying a wider role for PALs in the production of flavonoids, condensed tannins, benzenoids, and phenolic glycosides, in willow.

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Posted on 1 September 2015 | 6:00 am


Phenylethanoid glycosides in tepals of Magnolia salicifolia and their occurrence in flowers of Magnoliaceae

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Elaine A. Porter, Geoffrey C. Kite, Nigel C. Veitch, Ivey A. Geoghegan, Sonny Larsson, Monique S.J. Simmonds

Phenylethanoid glycosides were among the major UV-absorbing components in 80% aq. CH3OH extracts of the tepals of Magnolia salicifolia (Siebold & Zucc.) Maxim. (Magnoliaceae; Magnolia subgenus Yulania). Structural characterisation of isolated compounds by spectroscopic and chemical methods revealed three previously unrecorded examples, yulanoside A, yulanoside B and 2?-rhamnoechinacoside, and the known compounds echinacoside and crassifolioside; chromatographic methods also identified verbascoside in the tepal extract. Yulanoside A is the first reported example of a phenylethanoid pentaglycoside, namely hydroxytyrosol 1-O-{?-d-glucopyranosyl-(1?4)-?-d-glucopyranosyl-(1?6)-[3,4-dihydroxycinnamoyl-(?4)][?-l-rhamnopyranosyl-(1?3)][?-l-rhamnopyranosyl-(1?2)]-?-d-glucopyranoside}. A survey of Magnolia sensu lato and Liriodendron (the two genera of Magnoliaceae) suggested that yulanoside A and its deglucosyl derivative (yulanoside B) were a feature of the tepal chemistry of Magnolia subgenus Yulania (except Magnolia acuminata, the sole member of section Tulipastrum, which did not accumulate phenylethanoid glycosides). The two species of Liriodendron and examined examples of Magnolia subgenus Magnolia sections Magnolia and Rytidospermum (subsection Oyama) also accumulated phenylethanoid glycosides in their tepals and in these species, and in subgenus Yulania, the major compounds were one or more of echinacoside, 2?-rhamnoechinacoside, crassifolioside and verbascoside. Levels of phenylethanoid glycosides were found to be much lower in species studied from Magnolia sections Gwillimia, Macrophylla and Rytidospermum (subsection Rytidospermum), although yulanoside A was detectable in M. macrophylla and this may have some bearing on the placement of section Macrophylla, which is currently uncertain. In the isolates of yulanoside B and echinacoside, minor phenylethanoid glycosides were determined to be analogues of these compounds with ?-d-xylose at C-3? of the primary glucose rather than ?-l-rhamnose.

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Posted on 1 September 2015 | 6:00 am


Molecular and biochemical characterization of mannitol-1-phosphate dehydrogenase from the model brown alga Ectocarpus sp.

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Patricia Bonin, Agnès Groisillier, Alice Raimbault, Anaïs Guibert, Catherine Boyen, Thierry Tonon

The sugar alcohol mannitol is important in the food, pharmaceutical, medical and chemical industries. It is one of the most commonly occurring polyols in nature, with the exception of Archaea and animals. It has a range of physiological roles, including as carbon storage, compatible solute, and osmolyte. Mannitol is present in large amounts in brown algae, where its synthesis involved two steps: a mannitol-1-phosphate dehydrogenase (M1PDH) catalyzes a reversible reaction between fructose-6-phosphate (F6P) and mannitol-1-phosphate (M1P) (EC 1.1.1.17), and a mannitol-1-phosphatase hydrolyzes M1P to mannitol (EC 3.1.3.22). Analysis of the model brown alga Ectocarpus sp. genome provided three candidate genes for M1PDH activities. We report here the sequence analysis of Ectocarpus M1PDHs (EsM1PDHs), and the biochemical characterization of the recombinant catalytic domain of EsM1PDH1 (EsM1PDH1cat). Ectocarpus M1PDHs are representatives of a new type of modular M1PDHs among the polyol-specific long-chain dehydrogenases/reductases (PSLDRs). The N-terminal domain of EsM1PDH1 was not necessary for enzymatic activity. Determination of kinetic parameters indicated that EsM1PDH1cat displayed higher catalytic efficiency for F6P reduction compared to M1P oxidation. Both activities were influenced by NaCl concentration and inhibited by the thioreactive compound pHMB. These observations were completed by measurement of endogenous M1PDH activity and of EsM1PDH gene expression during one diurnal cycle. No significant changes in enzyme activity were monitored between day and night, although transcription of two out of three genes was altered, suggesting different levels of regulation for this key metabolic pathway in brown algal physiology.

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Posted on 1 September 2015 | 6:00 am


Alkaloid variation in New Zealand k?whai, Sophora species

Publication date: October 2015
Source:Phytochemistry, Volume 118

Author(s): Owen M. McDougal, Peter B. Heenan, Peter Jaksons, Catherine E. Sansom, Bruce M. Smallfield, Nigel B. Perry, John W. van Klink

Alkaloid contents of leaf and seed samples of eight species of Sophora native to New Zealand, plus Sophora cassioides from Chile are reported. Fifty-six leaf and forty-two seed samples were analysed for alkaloid content by proton nuclear magnetic resonance spectroscopy, which showed major alkaloids as cytisine, N-methyl cytisine and matrine. GC analyses quantified these and identified further alkaloid components. The alkaloids identified were cytisine, sparteine, and matrine-types common to Sophora from other regions of the world. Cytisine, N-methyl cytisine, and matrine were generally the most abundant alkaloids across all species with seeds containing the highest concentrations of alkaloids. However, there was no clear taxonomic grouping based on alkaloid composition. A quantitative analysis of various parts of two Sophora microphylla trees showed that the seeds were the richest source of alkaloids (total 0.4–0.5% DM), followed by leaf and twig (0.1–0.3%) and then bark (0.04–0.06%), with only low amounts (<0.02%) found in the roots. This study represents the most comprehensive phytochemical investigation of New Zealand Sophora species to date and presents data for three species of Sophora for which no prior chemistry has been reported.

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Posted on 1 September 2015 | 6:00 am


Molecular and biochemical characterization of the UDP-glucose: Anthocyanin 5-O-glucosyltransferase from Vitis amurensis

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Fei He, Wei-Kai Chen, Ke-Ji Yu, Xiang-Nan Ji, Chang-Qing Duan, Malcolm J. Reeves, Jun Wang

Generally, red Vitis vinifera grapes only contain monoglucosidic anthocyanins, whereas most non-vinifera red grapes of the Vitis genus have both monoglucosidic and bis-glucosidic anthocyanins, the latter of which are believed to be more hydrophilic and more stable. Although previous studies have established the biosynthetic mechanism for formation of monoglucosidic anthocyanins, less attention has been paid to that of bis-glucosidic anthocyanins. In the present research, the full-length cDNA of UDP-glucose: anthocyanin 5-O-glucosyltransferase from Vitis amurensis Rupr. cv. ‘Zuoshanyi’ grape (Va5GT) was cloned. After acquisition and purification of recombinant Va5GT, its enzymatic parameters were systematically analyzed in vitro. Recombinant Va5GT used malvidin-3-O-glucoside as its optimum glycosidic acceptor when UDP-glucose was used as the glycosidic donor. Va5GT-GFP was found to be located in the cytoplasm by analyzing its subcellular localization with a laser-scanning confocal fluorescence microscope, and this result was coincident with its metabolic function of modifying anthocyanins in grape cells. Furthermore, the relationship between the transcriptional expression of Va5GT and the accumulation of anthocyanidin bis-glucosides during berry development suggested that Va5GT is a key enzyme in the biosynthesis of bis-glucosidic anthocyanins in V. amurensis grape berries.

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Posted on 1 September 2015 | 6:00 am


The sesquiterpene lactone polymatin B from Smallanthus sonchifolius induces different cell death mechanisms in three cancer cell lines

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Christian De Ford, Jerónimo L. Ulloa, César A.N. Catalán, Alfredo Grau, Virginia S. Martino, Liliana V. Muschietti, Irmgard Merfort

A 8?-angeloyloxy-9?-hydroxy-14-oxo-acanthospermolide and five known melampolide sesquiterpene lactones (uvedalin, enhydrin, polymatin B, sonchifolin, and fluctuanin) were isolated from the leaves of Smallanthus sonchifolius. The compounds were identified by 1D-, 2D-NMR, HRMS, IR and UV analyses. In vitro cytotoxicity assays (MTT) showed that these sesquiterpene lactones display poor cytotoxic effects on peripheral blood mononuclear cells (PBMC) of healthy human subjects, whereas a strong cytotoxicity was observed in leukemia and pancreas cancer cells. For the mechanism of action of polymatin B, oxidative stress seems to be involved. Interestingly, reactive oxygen species (ROS) formation mainly induced different effects: apoptosis in CCRF-CEM cells, necroptosis in CEM-ADR5000 cells through induction of RIP1K, neither apoptosis nor necroptosis in MIA-PaCa-2 cells. Additionally, cells also died partly by necrosis.

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Posted on 1 September 2015 | 6:00 am


Single cell subtractive transcriptomics for identification of cell-specifically expressed candidate genes of pyrrolizidine alkaloid biosynthesis

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Christian Sievert, Till Beuerle, Julien Hollmann, Dietrich Ober

Progress has recently been made in the elucidation of pathways of secondary metabolism. However, because of its diversity, genetic information concerning biosynthetic details is still missing for many natural products. This is also the case for the biosynthesis of pyrrolizidine alkaloids. To close this gap, we tested strategies using tissues that express this pathway in comparison to tissues in which this pathway is not expressed. As many pathways of secondary metabolism are known to be induced by jasmonates, the pyrrolizidine alkaloid-producing species Heliotropium indicum, Symphytum officinale, and Cynoglossum officinale of the Boraginales order were treated with methyl jasmonate. An effect on pyrrolizidine alkaloid levels and on transcript levels of homospermidine synthase, the first specific enzyme of pyrrolizidine alkaloid biosynthesis, was not detectable. Therefore, a method was developed by making use of the often observed cell-specific production of secondary compounds. H. indicum produces pyrrolizidine alkaloids exclusively in the shoot. Homospermidine synthase is expressed only in the cells of the lower leaf epidermis and the epidermis of the stem. Suggesting that the whole pathway of pyrrolizidine alkaloid biosynthesis might be localized in these cells, we have isolated single cells of the upper and lower epidermis by laser-capture microdissection. The resulting cDNA preparations have been used in a subtractive transcriptomic approach. Quantitative real-time polymerase chain reaction has shown that the resulting library is significantly enriched for homospermidine-synthase-coding transcripts providing a valuable source for the identification of further genes involved in pyrrolizidine alkaloid biosynthesis.

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Posted on 1 September 2015 | 6:00 am


Flavonoid glycosides from the aerial parts of Acacia pennata in Myanmar

Publication date: October 2015
Source:Phytochemistry, Volume 118

Author(s): Anna Kim, Janggyoo Choi, Khin Myo Htwe, Young-Won Chin, Jinwoong Kim, Kee Dong Yoon

Phytochemical investigations of the aerial parts of Acacia pennata (Mimosaceae) from Myanmar led to the isolation of five flavonoid glycosides and six known compounds. The new compounds were identified as (2R,3S)-3,5,7-trihdyroxyflavan-3-O-?-l-rhamnopyranoside, (2S)-5,7-dihydroxyflavan-7-O-?-d-glucopyranoside-(4??8)-epiafzelechin-3-O-gallate, (2R)-4?,7-dihydroxyflavan-(4??8)-(2R,3S)-3,5,7-trihdyroxyflavan-3?-O-?-l-rhamnopyranoside, 5,7-dihydroxyflavone 6-C-?-boivinopyranosyl-7-O-?-d-glucopyranoside, and 5,7-dihydroxyflavone 7-O-?-d-glucopyranosyl-8-C-?-boivinopyranoside based on interpretation of spectroscopic data.

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Highlights

Five flavonoid glycoside (15) together with six known compounds were isolated from the aerial parts of Acacia pennata in Myamar. Their structures were determined by 1D, 2D NMR, UV, MS and CD data.





Posted on 1 September 2015 | 6:00 am


Biotic elicitors and mechanical damage modulate glucosinolate accumulation by co-ordinated interplay of glucosinolate biosynthesis regulators in polyploid Brassica juncea

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Rehna Augustine, Naveen C. Bisht

Glucosinolates are nitrogen and sulfur containing secondary metabolites found mainly in the Brassicaceae. They function as plant defense compounds against a broad spectrum of pathogens and pests. Since these molecules form part of the plant defense mechanism, glucosinolate biosynthesis may be modulated by environmental signals leading to activation of a biological stress response. In the current study, we have mimicked such conditions by exogenously applying biotic elicitors such as methyl jasmonate, salicylic acid, glucose and mechanical injury in Brassica juncea seedling over a time course experiment. We found that total glucosinolates over-accumulated under these stress conditions with maximum accumulation observed 24h post treatment. Indole glucosinolates like 1-methoxy-indol-3-ylmethyl and its precursor indol-3-methyl glucosinolates showed a more significant induction compared to aliphatic glucosinolates thereby suggesting a prominent role of indole glucosinolates during plant defense response in B. juncea seedlings. In contrast, the higher amounts of aliphatic glucosinolates were less regulated by the tested biotic elicitors in B. juncea. Expression profiling of multiple homologs of key transcriptional regulators of glucosinolate biosynthesis further showed that a complex interplay of these regulators exists in polyploid B. juncea where they exert co-ordinated and overlapping effects toward altering glucosinolate accumulation. This study has a significant role toward understanding and augmenting plant defense mechanisms in B. juncea, a globally important oilseed crop of genus Brassica.

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Methyl jasmonate, salicylic acid, glucose and wounding, factors mimicking biotic stress, enhances the accumulation of defense compound glucosinolates in Brassica juncea through co-ordinated interplay of glucosinolate regulators.





Posted on 1 September 2015 | 6:00 am


Functional characterization of a plastidal cation-dependent O-methyltransferase from the liverwort Plagiochasma appendiculatum

Publication date: October 2015
Source:Phytochemistry, Volume 118

Author(s): Rui-Xue Xu, Yu Zhao, Shuai Gao, Yu-Ying Zhang, Dan-Dan Li, Hong-Xiang Lou, Ai-Xia Cheng

Caffeoyl CoA O-methyltransferases (CCoAOMTs), known to be involved in phenylpropanoid metabolism and lignin synthesis, have been characterized from several higher plant species, which also harbor CCoAOMT-like enzymes responsible for methylation of a variety of flavonoids, anthocyanins, coumarins and phenylpropanoids. Here, a gene encoding a CCoAOMT (PaOMT1) was isolated from a sequenced cDNA library of the liverwort species Plagiochasma appendiculatum, a species belonging to the Family Aytoniaceae. The full-length cDNA sequence of PaOMT1 contains 909bp, and is predicted to encode a protein with 302 amino acids. The gene products were 40–50% identical to CCoAOMT sequences of other plants. Experiments based on recombinant PaOMT1 showed that the enzyme was able to methylate phenylpropanoids, flavonoids and coumarins, with a preference for the flavonoid quercetin (19). Although the substrate selectivity and biochemical feature of PaOMT1 is similar to CCoAOMT-like enzymes, the sequence alignment results indicated PaOMT1 is closer to true CCoAOMT enzymes. A phylogenetic analysis indicated that PaOMT1 is intermediate between true CCoAOMTs and CCoAOMT-like enzymes. The transient expression of a PaOMT1-GFP fusion in tobacco demonstrated that PaOMT1 is directed to the plastids. PaOMT1 may represent an ancestral form of higher plant true CCoAOMT and CCoAOMT-like enzymes. This is the first time an O-methyltransferase was characterized in liverworts.

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Posted on 1 September 2015 | 6:00 am


Analysis of aliphatic waxes associated with root periderm or exodermis from eleven plant species

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Dylan K. Kosma, Adam Rice, Mike Pollard

Aliphatic waxes can be found in association with suberized tissues, including roots. Non-polar lipids were isolated by rapid solvent extraction of mature regions of intact roots from eleven angiosperms, including both monocots and dicots. The majority of roots analyzed were taproots or tuberous taproots that had undergone secondary growth and thus were covered by a suberized periderm. The exceptions therein were maize (Zea mays L.) and rice (Oryza sativa L.), which present a suberized exodermis. The analysis herein focused on aliphatic waxes, with particular emphasis on alkyl hydroxycinnamates (AHCs). AHCs were widely distributed, absent from only one species, were found in both aerial and subterranean portions of tuberous taproots, and were associated with the fibrous roots of both maize and rice. Most species also contained monoacylglycerols, fatty alcohols and/or free fatty acids. Carrot (Daucus carrota L.) was the outlier, containing only free fatty acids, sterols, and polyacetylenes as identified components. Sterols were the only ubiquitous component across all roots analyzed. Monoacylglycerols of ?-hydroxy fatty acids were present in maize and rice root waxes. For species within the Brassiceae, wax compositions varied between subspecies or varieties and between aerial and subterranean portions of taproots. In addition, reduced forms of photo-oxidation products of ?-hydroxy oleate and its corresponding dicarboxylic acid (10,18-dihydroxy-octadec-8-enoate, 9,18-dihydroxy-octadec-10-enoate and 9-hydroxyoctadec-10-ene-1,18-dioate) were identified as naturally occurring suberin monomers in rutabaga (Brassica napus subsp. rapifera Metzg.) periderm tissues.

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Editorial Board/Publication Information

Publication date: September 2015
Source:Phytochemistry, Volume 117









Posted on 1 September 2015 | 6:00 am


Regulation of liver cell glucose homeostasis by dehydroabietic acid, abietic acid and squalene isolated from balsam fir (Abies balsamea (L.) Mill.) a plant of the Eastern James Bay Cree traditional pharmacopeia

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Abir Nachar, Ammar Saleem, John T. Arnason, Pierre S. Haddad

In our previous study, Abies balsamea (L.) Mill., a plant used in Cree traditional medicine, had a strong effect on the regulation of glucose homeostasis in liver cells. This study aimed to isolate and identify its active constituents using a bioassay-guided fractionation approach as well as to elucidate their mechanism(s) of action. The effect of the crude extract and its constituents was evaluated on the activity of Glucose-6-Phosphatase (G6Pase) and Glycogen Synthase (GS) and phosphorylation of three kinases, AMP-activated protein kinase (AMPK), Akt and Glycogen Synthase Kinase-3 (GSK-3). Three compounds, abietic acid, dehydroabietic acid and squalene, were isolated from the most active fraction in the bioassays (hexane). The compounds were able to decrease the activity of G6Pase and to stimulate GS. Their effect on G6Pase activity involved both Akt and AMPK phosphorylation with significant correlations between insulin-dependent and -independent pathways and the bioassay. In addition, the compounds were able to stimulate GS through GSK-3 phosphorylation with a significant correlation between the signaling pathway and the bioassay. Dehydroabietic acid stood out for its strongest effect in all the experiments close to that of the crude extract. These compounds may have potential applications in the treatment of type 2 diabetes and insulin resistance.

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Posted on 1 September 2015 | 6:00 am


Isolation and identification of Desmodium root exudates from drought tolerant species used as intercrops against Striga hermonthica

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): A.M. Hooper, J.C. Caulfield, B. Hao, J.A. Pickett, C.A.O. Midega, Z.R. Khan

Plants from the genus Desmodium, in particular D. uncinatum, are used on sub-Saharan small-holder farms as intercrops to inhibit parasitism of cereal crops by Striga hermonthica and Striga asiatica via an allelopathic mechanism. The search for Desmodium species which are adapted to more arid conditions, and which show resilience to increased drought stress, previously identified D. intortum, D. incanum and D. ramosissimum as potential drought tolerant intercrops. Their potential as intercrops was assessed for resource poor areas of rain-fed cereal production where drought conditions can persist through normal meteorological activity, or where drought may have increasing impact through climate change. The chemical composition of the root exudates were characterised and the whole exudate biological activity was shown to be active in pot experiments for inhibition of Striga parasitism on maize. Furthermore, rain fed plot experiments showed the drought tolerant Desmodium intercrops to be effective for Striga inhibition. This work demonstrates the allelopathic nature of the new drought tolerant intercrops through activity of root exudates and the major compounds seen in the exudates are characterised as being C-glycosylflavonoid. In young plants, the exudates show large qualitative differences but as the plants mature, there is a high degree of convergence of the C-glycosylflavonoid exudate chemical profile amongst active Desmodium intercrops that confers biological activity. This defines the material for examining the mechanism for Striga inhibition.

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4-Methoxycinnamic acid – An unusual phenylpropanoid involved in phenylphenalenone biosynthesis in Anigozanthos preissii

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): William Hidalgo, Marco Kai, Bernd Schneider

In vitro root cultures of Anigozanthos preissii and Wachendorfia thyrsiflora (Haemodoraceae) are suitable biological systems for studying the biosynthesis of phenylphenalenones. Here we report how we used these root cultures to investigate precursor–product relationships between phenylpropanoids and phenylphenalenones whose phenyl rings share identical substitution patterns. Four phenylpropanoic acids, including ferulic acid and the unusual 4-methoxycinnamic acid, were used in 13C-labeled form as substrates to study their incorporation into phenylphenalenones. In addition to the previously reported 2-hydroxy-9-(4?-hydroxy-3?-methoxyphenyl)-1H-phenalen-1-one (trivial name musanolone F), 2-hydroxy-9-(4?-methoxyphenyl)-1H-phenalen-1-one (proposed trivial name 4?-methoxyanigorufone) was found as a biosynthetic product in A. preissii. The carbon skeleton of 4?-methoxycinnamic acid was biosynthetically incorporated as an intact unit including its 4?-O-methyl substituent at the lateral phenyl ring. 4?-Methoxyanigorufone is reported here for the first time as a natural product.

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Graphical Contents List

Publication date: September 2015
Source:Phytochemistry, Volume 117









Posted on 1 September 2015 | 6:00 am


Profiling of primary metabolites and flavonols in leaves of two table grape varieties collected from semiarid and temperate regions

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Jamil Harb, Saleh Alseekh, Takayuki Tohge, Alisdair R. Fernie

Cultivation of grapes in West Bank – Palestine is very old and a large number of grape varieties exist as a result of continuous domestication over thousands of years. This rich biodiversity has highly influenced the consumer behavior of local people, who consume both grape berries and leaves. However, studies that address the contents of health-promoting metabolites in leaves are scarce. Accordingly the aim of this study is to assess metabolite levels in leaves of two grape varieties that were collected from semiarid and temperate regions. Metabolic profiling was conducted using GC–MS and LC–MS. The obtained results show that abiotic stresses in the semiarid region led to clear changes in primary metabolites, in particular in amino acids, which exist at very high levels. By contrast, qualitative and genotype-dependent differences in secondary metabolites were observed, whereas abiotic stresses appear to have negligible effect on the content of these metabolites. The qualitative difference in the flavonol profiles between the two genotypes is most probably related to differential expression of specific genes, in particular flavonol 3-O-rhamnosyltransferase, flavonol-3-O-glycoside pentosyltransferases and flavonol-3-O- d -glucoside l -rhamnosyltransferase by ‘Beituni’ grape leaves, which led to much higher levels of flavonols with rutinoside, pentoside, and rhamnoside moieties with this genotype.

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Posted on 1 September 2015 | 6:00 am


Grayanane and leucothane diterpenoids from the leaves of Rhododendron micranthum

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Mengke Zhang, Yangyang Xie, Guanqun Zhan, Liang Lei, Penghua Shu, Yongli Chen, Yongbo Xue, Zengwei Luo, Qian Wan, Guangmin Yao, Yonghui Zhang

Eleven grayanane diterpenoids, 1-epi-grayanotoxin IV, 1-epi-grayanotoxin II, 6-deoxy-1-epi-grayanotoxin XVII, 6-deoxygrayanotoxin XVII, 16-acetylgrayanotoxin II, 3-oxograyanotoxin IX, 14-deoxygrayanotoxin VIII, 14-acetylisograyanotoxin II, rhodomicranols C–E, and a leucothane diterpenoid, rhodomicranol F, together with eleven known diterpenoids were isolated from leaves of Rhododendron micranthum. Their structures were elucidated by spectroscopic analyses, with the absolute configurations of 1-epi-grayanotoxin IV and rhodomicranol C determined by single-crystal X-ray diffraction with Cu K? radiation, and the structures of 14-acetylisograyanotoxin II and known grayanotoxins IX and X confirmed by single-crystal X-ray diffraction. All twenty-three diterpenoids were evaluated for their in vitro immunomodulatory activities, and none showed significant immunomodulatory activities in a dose-dependent manner. In addition, they are non-toxic to the murine lymphocytes in the general cytotoxicity assay.

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Abscisic acid induces biosynthesis of bisbibenzyls and tolerance to UV-C in the liverwort Marchantia polymorpha

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Akito Kageyama, Kimitsune Ishizaki, Takayuki Kohchi, Hideyuki Matsuura, Kosaku Takahashi

Environmental stresses are effective triggers for the biosynthesis of various secondary metabolites in plants, and phytohormones such as jasmonic acid and abscisic acid are known to mediate such responses in flowering plants. However, the detailed mechanism underlying the regulation of secondary metabolism in bryophytes remains unclear. In this study, the induction mechanism of secondary metabolites in the model liverwort Marchantia polymorpha was investigated. Abscisic acid (ABA) and ultraviolet irradiation (UV-C) were found to induce the biosynthesis of isoriccardin C, marchantin C, and riccardin F, which are categorized as bisbibenzyls, characteristic metabolites of liverworts. UV-C led to the significant accumulation of ABA. Overexpression of MpABI1, which encodes protein phosphatase 2C (PP2C) as a negative regulator of ABA signaling, suppressed accumulation of bisbibenzyls in response to ABA and UV-C irradiation and conferred susceptibility to UV-C irradiation. These data show that ABA plays a significant role in the induction of bisbibenzyl biosynthesis, which might confer tolerance against UV-C irradiation in M. polymorpha.

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Highlights

ABA and UV-C induced the biosynthesis of bisbibenzyls in the model liverwort Marchantia polymorpha, and UV-C irradiation was severely damaging to the MpABI1 overexpressor.





Posted on 1 September 2015 | 6:00 am


Gingerols and shogaols: Important nutraceutical principles from ginger

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Ruchi Badoni Semwal, Deepak Kumar Semwal, Sandra Combrinck, Alvaro M. Viljoen

Gingerols are the major pungent compounds present in the rhizomes of ginger (Zingiber officinale Roscoe) and are renowned for their contribution to human health and nutrition. Medicinal properties of ginger, including the alleviation of nausea, arthritis and pain, have been associated with the gingerols. Gingerol analogues are thermally labile and easily undergo dehydration reactions to form the corresponding shogaols, which impart the characteristic pungent taste to dried ginger. Both gingerols and shogaols exhibit a host of biological activities, ranging from anticancer, anti-oxidant, antimicrobial, anti-inflammatory and anti-allergic to various central nervous system activities. Shogaols are important biomarkers used for the quality control of many ginger-containing products, due to their diverse biological activities. In this review, a large body of available knowledge on the biosynthesis, chemical synthesis and pharmacological activities, as well as on the structure–activity relationships of various gingerols and shogaols, have been collated, coherently summarised and discussed. The manuscript highlights convincing evidence indicating that these phenolic compounds could serve as important lead molecules for the development of therapeutic agents to treat various life-threatening human diseases, particularly cancer. Inclusion of ginger or ginger extracts in nutraceutical formulations could provide valuable protection against diabetes, cardiac and hepatic disorders.

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Posted on 1 September 2015 | 6:00 am


Prevalence and specificity of Baeyer–Villiger monooxygenases in fungi

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Lorena Butinar, Martina Mohor?i?, Valérie Deyris, Katia Duquesne, Gilles Iacazio, Magalie Claeys-Bruno, Josepha Friedrich, Véronique Alphand

Out of 107 fungal strains belonging to three phyla (Ascomycota, Basidiomycota and Zygomycota) and 46 genera, 86 exhibited Baeyer–Villiger monooxygenase (BVMO) activity against racemic bicyclo[3.2.0]heptenone. The strains were classified into three “profiles” based on regio- and enantioselectivity. Statistical analyses of our results, extended by literature data, showed that these profiles could be related to the taxonomic classification of the strains, and suggest that the BVMOs from the Zygomycota phylum may be different in their primary structures from established ones.

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Posted on 1 September 2015 | 6:00 am


Flavonoids from Piper delineatum modulate quorum-sensing-regulated phenotypes in Vibrio harveyi

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Alberto J. Martín-Rodríguez, Juan C. Ticona, Ignacio A. Jiménez, Ninoska Flores, José J. Fernández, Isabel L. Bazzocchi

Quorum sensing (QS), or bacterial cell-to-cell communication, is a key process for bacterial colonization of substrata through biofilm formation, infections, and production of virulence factors. In an ongoing investigation of bioactive secondary metabolites from Piper species, four new flavonoids (14), along with five known ones (59) were isolated from the leaves of Piper delineatum. Their stereostructures were established by spectroscopic and spectrometric methods, including 1D and 2D NMR experiments, and comparison with data reported in the literature. The compounds were screened for their ability to interfere with QS signaling in the bacterial model Vibrio harveyi. Four compounds from this series (2, 3, 6, and 7) exhibited remarkable activity in the micromolar range, being compounds 3 and 7 particularly attractive since they did not affect bacterial growth. The results suggest that these flavonoids disrupt QS-mediated bioluminescence by interaction with elements downstream LuxO in the QS circuit of V. harveyi, and also, they exhibited a strong dose-dependent inhibition of biofilm formation. The present findings shed light on the QS inhibition mechanisms of flavonoids, underlining their potential applications.

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Structure and cytotoxic activity of sesquiterpene glycoside esters from Calendula officinalis L.: Studies on the conformation of viridiflorol

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Michele D’Ambrosio, Alexandru Ciocarlan, Elisa Colombo, Antonio Guerriero, Cosimo Pizza, Enrico Sangiovanni, Mario Dell’Agli

Topic applications of Calendula officinalis L. lipophilic extracts are used in phytotherapy to relieve skin inflammatory conditions whereas infusions are used as a remedy for gastric complaints. Such a different usage might be explained by some cytotoxicity of lipophilic extracts at gastric level but little is known about this. Therefore, we screened the CH2Cl2 extract from the flowers of C. officinalis by MTT and LDH assays in human epithelial gastric cells AGS. This bioassay-oriented approach led to the isolation of several sesquiterpene glycosides which were structurally characterized by spectroscopic measurements, chemical reactions and MM calculations. The conformational preferences of viridiflorol fucoside were established and a previously assigned stereochemistry was revised. The compounds 1a, 2a and 3f showed comparably high cytotoxicity in the MTT assays, whereas the effect on LDH release was lower. Our study provides new insights on the composition of C. officinalis extracts of medium polarity and identifies the main compounds that could be responsible for cytotoxic effects at gastric level.

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Highlights

The sesquiterpene glycoside esters are responsible for cytotoxic effects of extracts of C. officinalis. Their structures were established by spectroscopic methods, chemical reactions and molecular mechanic calculations.





Posted on 1 September 2015 | 6:00 am


Toxic proteins in plants

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Liuyi Dang, Els J.M. Van Damme

Plants have evolved to synthesize a variety of noxious compounds to cope with unfavorable circumstances, among which a large group of toxic proteins that play a critical role in plant defense against predators and microbes. Up to now, a wide range of harmful proteins have been discovered in different plants, including lectins, ribosome-inactivating proteins, protease inhibitors, ureases, arcelins, antimicrobial peptides and pore-forming toxins. To fulfill their role in plant defense, these proteins exhibit various degrees of toxicity towards animals, insects, bacteria or fungi. Numerous studies have been carried out to investigate the toxic effects and mode of action of these plant proteins in order to explore their possible applications. Indeed, because of their biological activities, toxic plant proteins are also considered as potentially useful tools in crop protection and in biomedical applications, such as cancer treatment. Genes encoding toxic plant proteins have been introduced into crop genomes using genetic engineering technology in order to increase the plant’s resistance against pathogens and diseases. Despite the availability of ample information on toxic plant proteins, very few publications have attempted to summarize the research progress made during the last decades. This review focuses on the diversity of toxic plant proteins in view of their toxicity as well as their mode of action. Furthermore, an outlook towards the biological role(s) of these proteins and their potential applications is discussed.

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Botryane, noreudesmane and abietane terpenoids from the ascomycete Hypoxylon rickii

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Eric Kuhnert, Frank Surup, Vincent Wiebach, Steffen Bernecker, Marc Stadler

In the course of our screening for new bioactive natural products, a culture of Hypoxylon rickii, a xylariaceous ascomycete collected from the Caribbean island Martinique, was identified as extraordinary prolific producer of secondary metabolites. Ten metabolites of terpenoid origin were isolated from submerged cultures of this species by preparative HPLC. Their structures were elucidated using spectral techniques including 2D NMR and HRESIMS. Three of the compounds were elucidated as new botryanes (13) along with three known ones, i.e. (3aS)-3a,5,5,8-tetramethyl-3,3a,4,5-tetrahydro-1H-cyclopenta[de]isochromen-1-one (4), (3aS,8R)-3a,5,5,8-tetramethyl-3,3a,4,5,7,8-hexahydro-1H-cyclopenta[de]isochromen-1-one (5) and botryenanol (6). Further three new sesquiterpenoids featured a 14-noreudesmane-type skeleton and were named hypoxylan A–C (79); the diterpenoid rickitin A (10) contains an abietane-type backbone. Compounds 1, 2, 3, 7, and 10 showed cytotoxic effects against murine cells.

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Highlights

Ten terpenoids, among those seven novel natural products, were isolated from cultures of the tropical ascomycete Hypoxylon rickii (Xylariaceae). Their structures were elucidated using 2D NMR and HRESIMS. The new compounds belong to the botryane, 14-noreudesmane and abietane types. Compounds 1, 2, 3, 7, and 10 showed cytotoxic effects against murine cells.





Posted on 1 September 2015 | 6:00 am


Sesquiterpenes, flavonoids, shikimic acid derivatives and pyrrolizidine alkaloids from Senecio kingii Hook

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Liliana Ruiz-Vásquez, Matías Reina, M. López-Rodríguez, Cristina Giménez, Raimundo Cabrera, Pedro Cuadra, Víctor Fajardo, Azucena González-Coloma

Twenty-four compounds including eleven eremophilanolides (111), one eremophilane (13), five shikimic acid derivatives (1418), six flavonoids (1924), and the macrocyclic unsaturated pyrrolizidine alkaloid integerrimine (25) were isolated from Senecio kingii, an endemic species from the Magallanes Region (Chile). Compounds 3, 5, 6, 811 and 1318 have not been previously reported as natural products. Their molecular structures were determined by NMR spectroscopic analysis and comparison with published NMR data. An X-ray-analysis of compound 3 has been performed. Their insecticidal and antifungal activities were tested, being compound 3 the strongest insect antifeedant. Compounds 6, 9 and 18 were moderate antifungals.

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Prenylated flavanone derivatives isolated from Erythrina addisoniae are potent inducers of apoptotic cell death

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Claus M. Passreiter, Anke-Katrin Suckow-Schnitker, Andreas Kulawik, Jonathan Addae-Kyereme, Colin W. Wright, Wim Wätjen

Extracts of Erythrina addisoniae are frequently used in the traditional medicine of Western Africa, but insufficient information about active compounds is available. From the stem bark of E. addisoniae, three (1, 2, 4) and three known (3, 5, 6) flavanones were isolated: addisoniaflavanones I and II, containing either a 2?,3?-epoxyprenyl moiety (1) or a 2?,3?-dihydroxyprenyl moiety (2) were shown to be highly toxic (MTT assay: EC50 values of 5.25±0.7 and 8.5±1.3?M, respectively) to H4IIE hepatoma cells. The cytotoxic potential of the other isolated flavanones was weaker (range of EC50 values between 15 and >100?M). Toxic effects of addisoniaflavanone I and II were detectable after 3h (MTT assay). Both compounds induced an apoptotic cell death (caspase-3/7 activation, nuclear fragmentation) in the hepatoma cells and, at high concentrations, also necrosis (membrane disruption: ethidium bromide staining). Formation of DNA strand breaks was not detectable after incubation with these compounds (comet assay). In conclusion, the prenylated flavanones addisoniaflavanones I and II may be of interest for pharmacological purposes due to their high cytotoxic and pro-apoptotic potential against hepatoma cells.

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Posted on 1 September 2015 | 6:00 am


Low temperature tolerance in plants: Changes at the protein level

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Mohsen Janmohammadi, Lello Zolla, Sara Rinalducci

Low temperature (LT) is one of several important environmental stresses influencing plant performance and distribution. Adaptation to LT is a highly dynamic stress-response phenomenon and involves complex cross-talk between different regulatory levels. Although plants differ in their sensitivity to LT, in temperate species low nonfreezing temperatures cause noticeable alterations in various biochemical and physiological processes that can potentially improve freezing tolerance. This adaptation is associated with changes in the expression pattern of genes and their protein products. Proteins are the major players in most cellular events and are directly involved in plant LT responses, thereby proteome analysis could help uncover additional novel proteins associated with LT tolerance. Proteomics is recommended as an appropriate strategy for complementing transcriptome level changes and characterizing translational and post-translational regulations. In this review, we considered alterations in the expression and accumulation of proteins in response to LT stress in the three major cereal crops produced worldwide (wheat, barley, and rice). LT stress down-regulates many photosynthesis-related proteins. On the contrary, pathways/protein sets that are up-regulated by LT include carbohydrate metabolism (ATP formation), ROS scavenging, redox adjustment, cell wall remodelling, cytoskeletal rearrangements, cryoprotection, defence/detoxification. These modifications are common adaptation reactions also observed in the plant model Arabidopsis, thus representing key potential biomarkers and critical intervention points for improving LT tolerance of crop plants in cold regions with short summers. We believe that an assessment of the proteome within a broad time frame and during the different phenological stages may disclose the molecular mechanisms related to the developmental regulation of LT tolerance and facilitate the progress of genetically engineered stress-resistant plant varieties.

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Posted on 1 September 2015 | 6:00 am


Anti-inflammation furanoditerpenoids from Caesalpinia minax Hance

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Ruijuan Dong, Jiuzhi Yuan, Shilong Wu, Jian Huang, Xiaotong Xu, Zhaohua Wu, Huiyuan Gao

Cassane skeletons are rare in nature, but often possess valuable medicinal properties. A furanoditerpenoid with an unusual A-seco-rearranged cassane skeleton, neocaesalminin A, and five furanoditerpenoids were isolated from seeds of Caesalpinia minax Hance, along with six known cassane derivatives, 7-O-acetyl-bonducellpin C, caesalmin F, caesalmin C, ?-caesalmin, caesalmin E1 and caesalpinin K. Compound structures were determined by spectroscopy (HR-ESI-MS, UV, IR, 1D NMR, 2D NMR), X-ray crystallography and quantum chemical computation of electronic circular dichroism). Three of the previously known compounds exhibited significant inhibition of nitric oxide production of RAW264.7 macrophages stimulated by lipopolysaccharide (LPS).

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Highlights

Twelve furanocassane derivatives, including six previously unreported were isolated from the seeds of Caesalpinia minax Hance. Neocaesalminin A (1) was found with an unusual A-seco-rearranged cassane skeleton. The inhibitory effect on NO production for all compounds was evaluated in vitro. Furanoditerpenes were responsible for this herb’s anti-inflammation activity.





Posted on 1 September 2015 | 6:00 am


Sulfated phenolic acids from Dasycladales siphonous green algae

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Caroline Kurth, Matthew Welling, Georg Pohnert

Sulfated aromatic acids play a central role as mediators of chemical interactions and physiological processes in marine algae and seagrass. Among others, Dasycladus vermicularis (Scopoli) Krasser 1898 uses a sulfated hydroxylated coumarin derivative as storage metabolite for a protein cross linker that can be activated upon mechanical disruption of the alga. We introduce a comprehensive monitoring technique for sulfated metabolites based on fragmentation patterns in liquid chromatography/mass spectrometry and applied it to Dasycladales. This allowed the identification of two new aromatic sulfate esters 4-(sulfooxy)phenylacetic acid and 4-(sulfooxy)benzoic acid. The two metabolites were synthesized to prove the mass spectrometry-based structure elucidation in co-injections. We show that both metabolites are transformed to the corresponding desulfated phenols by sulfatases of bacteria. In biofouling experiments with Escherichia coli and Vibrio natriegens the desulfated forms were more active than the sulfated ones. Sulfatation might thus represent a measure of detoxification that enables the algae to store inactive forms of metabolites that are activated by settling organisms and then act as defense.

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Posted on 1 September 2015 | 6:00 am


Natural lignans from Arctium lappa as antiaging agents in Caenorhabditis elegans

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Shan Su, Michael Wink

Arctium lappa is a well-known traditional medicinal plant in China (TCM) and Europe that has been used for thousands of years to treat arthritis, baldness or cancer. The plant produces lignans as secondary metabolites, which have a wide range of bioactivities. Yet, their antiaging potential has not been explored. In this study, we isolated six lignans from A. lappa seeds, namely arctigenin, matairesinol, arctiin, (iso)lappaol A, lappaol C, and lappaol F. The antioxidant and antiaging properties of the isolated lignans were studied using Caenorhabditis elegans as a relevant animal model. All lignans at concentrations of 10 and 100?M significantly extended the mean life span of C. elegans. The strongest effect was observed with matairesinol, which at a concentration of 100?M extended the life span of worms by 25%. Additionally, we observed that five lignans are strong free radical-scavengers in vitro and in vivo and all lignans can improve survival of C. elegans under oxidative stress. Furthermore, the lignans can induce the nuclear translocation of the transcription factor DAF-16 and up-regulate its expression, suggesting that a possible underlying mechanism of the observed longevity-promoting activity of lignans depends on DAF-16 mediated signaling pathway. All lignans up-regulated the expression of jnk-1, indicating that lignans may promote the C. elegans longevity and stress resistance through a JNK-1-DAF-16 cascade. Our study reports new antiaging activities of lignans, which might be candidates for developing antiaging agents.

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Posted on 1 September 2015 | 6:00 am


Plant betalains: Chemistry and biochemistry

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Mohammad Imtiyaj Khan, P. Giridhar

Betalains are vacuolar pigments composed of a nitrogenous core structure, betalamic acid [4-(2-oxoethylidene)-1,2,3,4-tetrahydropyridine-2,6-dicarboxylic acid]. Betalamic acid condenses with imino compounds (cyclo-l-3,4-dihydroxy-phenylalanine/its glucosyl derivatives), or amino acids/derivatives to form variety of betacyanins (violet) and betaxanthins (yellow), respectively. About 75 betalains have been structurally unambiguously identified from plants of about 17 families (known till date) out of 34 families under the order Caryophyllales, wherein they serve as chemosystematic markers. In this review, all the identified betalain structures are presented with relevant discussion. Also, an estimated annual production potential of betalains has been computed for the first time. In addition, mutual exclusiveness of anthocyanins and betalains has been discussed in the wake of new evidences. An inclusive list of betalain-accumulating plants reported so far has been presented here to highlight pigment occurrence and accumulation pattern. Betalain synthesis starts with hydroxylation of tyrosine to DOPA, and subsequent cleavage of aromatic ring of DOPA resulting to betalamic acid formation. This pathway consists of two key enzymes namely, bifunctional tyrosinase (hydroxylation and oxidation) and DOPA dioxygenase (O2-dependent aromatic ring cleavage). Various spontaneous cyclisation, condensation and glucosylation steps complement the extended pathway, which has been presented here comprehensively. The biosynthesis is affected by various ecophysiological factors including biotic and abiotic elicitors that can be manipulated to increase pigment production for commercial scale extraction. Betalains are completely safe to consume, and contribute to health.

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Posted on 1 September 2015 | 6:00 am


Chemical constituents derived from Artocarpus xanthocarpus as inhibitors of melanin biosynthesis

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Yu-Jing Jin, Cha-Chi Lin, Tzy-Ming Lu, Jih-Heng Li, Ih-Sheng Chen, Yueh-Hsiung Kuo, Horng-Huey Ko

Twenty-four compounds, including the previously unknown artoxanthocarpuone A, artoxanthocarpuone B, hydroxylakoochin A, methoxylakoochin A, epoxylakoochin A, and artoxanthol, were isolated and characterized spectroscopically. Among them, artoxanthol is stilbene oligomer presumably constructed in a 5,11,12-triphenyl hexahydrochrysene scaffold by a Diels–Alder type of reaction, for which a biosynthetic pathway is proposed. Artoxanthol, alboctalol, steppogenin, norartocarpetin, resveratrol, oxyresveratrol, and chlorophorin potently inhibited mushroom tyrosinase activity with IC50 values from 0.9 to 5.7?M that were all far stronger than the positive controls. Artoxanthocarpuone A, artoxanthocarpuone B, methoxylakoochin A, lakoochin A, cudraflavone C, artonin A, resveratrol, and chlorophorin reduced tyrosinase activity and inhibited ?-melanocyte-stimulating hormone-induced melanin production in B16F10 melanoma cells without affecting cell proliferation. Collectively, the results suggest that the constituents of Artocarpus xanthocarpus have potential to be used as depigmentation agents.

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Highlights

Six previously unknown compounds and 18 known compounds from Artocarpus xanthocarpus were isolated and characterized spectroscopically. Their anti-melanogenesis activity were evaluated in B16F10 melanoma cells. The results indicated that some of these constituents may be a candidate for the depigmentation agents.





Posted on 1 September 2015 | 6:00 am


Phytotoxins produced by Phoma chenopodiicola, a fungal pathogen of Chenopodium album

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Marco Evidente, Alessio Cimmino, Maria Chiara Zonno, Marco Masi, Alexander Berestetskyi, Ernesto Santoro, Stefano Superchi, Maurizio Vurro, Antonio Evidente

Two phytotoxins were isolated from the liquid culture of Phoma chenopodiicola, a fungal pathogen proposed for the biological control of Chenopodium album, a common worldwide weed of arable crops. The two phytotoxins appeared to be a new tetrasubstituted furopyran and a new ent-pimaradiene. From the same culture a new tetrasubstituted isocoumarin was also isolated. These compounds were characterized by using spectroscopic (essentially 1D and 2D NMR and HR ESI MS) and chemical methods as 3-(3-methoxy-2,6-dimethyl-7aH-furo[2,3-b]pyran-4-yl)-but-2-en-1-ol (chenopodolan D, 1) (1S,2S,3S,4S,5S,9R,10S,12S,13S)-1,3,12-triacetoxy-2,hydroxy-6-oxo-ent-pimara-7(8),15-dien-18-oic acid 2,18-lactone (chenopodolin B, 3), and, 4,5,7-trihydroxy-3-methyl-isochroman-1-one (chenisocoumarin, 2) The absolute configuration of chenisocoumarin was assigned by applying an advanced Mosher’s method through the derivatization of its secondary hydroxylated carbon C-4, while that of chenopodolan D by application of quantum mechanical calculations of chiroptical (ECD and ORD) properties. When assayed by leaf puncture against non-host weeds, chenopodolan D and chenopodolin B showed phytotoxicity while chenisocoumarin and the 9-O-acetyl derivative of chenopodolan D were inactive. These results confirm that the nature of the side chain at C-4 in chenopodolans, and in particular its hydroxylation, are important features for activity. The activity of chenopodolin B could also be explained by its possible hydrolysis to chenopodolin.

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Posted on 1 September 2015 | 6:00 am


Cytotoxic diterpenoids from Jatropha curcas cv. nigroviensrugosus CY Yang Roots

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): JieQing Liu, YuanFeng Yang, JianJun Xia, XuYang Li, ZhongRong Li, Lin Zhou, MingHua Qiu

An investigation of phytochemicals from the roots of Jatropha curcas cv. nigroviensrugosus resulted in the isolation of twenty diterpenoids, including lathyranlactone, an unusual diterpenoid lactone possessing a 5/13/3 tricyclic skeleton, jatrocurcasenones A–E and jatrophodiones B–E, as well as 10 known analogues. All isolates were evaluated for cytotoxicity against the HL-60, SMMC-772, A-549, MCF-7 and SW480 human tumor cell lines using the MTS viability assay. Four of the known analogues showed cytotoxic activity in these cell lines, with IC50 values ranging from 2.0 to 23.0?M. Moreover, the assessment of their cytotoxic structure–activity relationships showed the epoxy ring between C-5 and C-6 and the hydroxyl group at C-2 were the key functionalities for cytotoxicity.

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Posted on 1 September 2015 | 6:00 am


Indole-3-acetic acid UDP-glucosyltransferase from immature seeds of pea is involved in modification of glycoproteins

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Maciej Ostrowski, Anna Hetmann, Anna Jakubowska

The glycosylation of auxin is one of mechanisms contributing to hormonal homeostasis. The enzyme UDPG: indole-3-ylacetyl-?-d-glucosyltransferase (IAA glucosyltransferase, IAGlc synthase) catalyzes the reversible reaction: IAA+UDPG?1-O-IA-glucose+UDP, which is the first step in the biosynthesis of IAA-ester conjugates in monocotyledonous plants. In this study, we report IAA-glucosyltransferase isolated using a biochemical approach from immature seed of pea (Pisum sativum). The enzyme was purified by PEG fractionation, DEAE-Sephacel anion-exchange chromatography and preparative PAGE. LC–MS/MS analysis of tryptic peptides of the enzyme revealed the high identity with maize IAGlc synthase, but lack of homology with other IAA-glucosyltransferases from dicots. Biochemical characterization showed that of several acyl acceptors tested, the enzyme had the highest activity on IAA as the glucosyl acceptor (K m =0.52mM, V max =161nmolmin?1, k cat/K m =4.36mMs?1) and lower activity on indole-3-propionic acid and 1-naphthalene acetic acid. Whereas indole-3-butyric acid and indole-3-propionic acid were competitive inhibitors of IAGlc synthase, d-gluconic acid lactone, an inhibitor of ?-glucosidase activity, potentiated the enzyme activity at the optimal concentration of 0.3mM. Moreover, we demonstrated that the 1-O-IA-glucose synthesized by IAGlc synthase is the substrate for IAA labeling of glycoproteins from pea seeds indicating a possible role of this enzyme in the covalent modification of a class of proteins by a plant hormone.

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Posted on 1 September 2015 | 6:00 am


Antrocarines A–F, antiplasmodial ergostane steroids from the stem bark of Antrocaryon klaineanum

Publication date: September 2015
Source:Phytochemistry, Volume 117

Author(s): Pascal D. Douanla, Turibio Kuiate Tabopda, Alembert T. Tchinda, Ewa Cieckiewicz, Michel Frédérich, Fabrice Fekam Boyom, Nole Tsabang, Samuel Yeboah, Augustin E. Nkengfack, Marguerite Hortence K. Tchuendem

During a study on the chemistry and biological activity of Antrocaryon klaineanum Pierre, six new sterols including 4,24(28)-ergostadiene-6?,7?-diol (1), 6?-methoxy-4,24(28)-ergostadiene-7?,20S-diol (2), 6?-methoxy-4,24(28)-ergostadien-7?-ol (3), 20S-hydroxy-24(28)-ergosten-3-one (4), 7?-hydroxy-4,24(28)-ergostadien-3-one (5), and 24(28)-ergostene-3?,6?-diol (6) were characterized by physical and spectroscopic means. The known steroids 7 and 8 were also isolated. The crude extract and the isolated compounds were evaluated for their ability to inhibit the 3D7 strain of Plasmodium falciparum. Compounds 2, 3, and 8 showed potent activity while that of the crude extract was moderate.

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Posted on 1 September 2015 | 6:00 am





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