Phytochemistry (v.70, #1)
Graphical Contents List (1-6).
The role of tryptophan as a biosynthetic precursor of indole-diterpenoid fungal metabolites: Continuing a debate by Peter G. Mantle (7-10).
Whereas the first 14C-labelling studies indicated that the indole moiety of fungal indole-diterpenoids came from tryptophan, recent 13C-labelling has persuaded acceptance that indole-3-glycerol phosphate is the source instead. Reasoning, questioning suitability of the latter’s protocol, is presented and experimental strategies for clarifying the present situation are proposed.Studies in the 1980s and 1990s on the origin of the indole moiety in fungal indole-diterpenoids using 14C-labelled tryptophan consistently showed autoradiographic evidence but gave low % incorporation of the probe. Recent studies on a member of the group (nodulisporic acid A), using more specific 13C methodology, demonstrated a role of the tryptophan biosynthetic pathway but, in failing to show involvement of end-product, concluded that the indole was derived from indole-3-glycerol phosphate and suggested that the previous 14C data arose via metabolic scrambling of label. In considering the protocol for the 13C studies, there is concern that the fungal material was starved of an exogenous nitrogen source and thus could have degraded added labelled tryptophan. Consequently, synthesis of the serine necessary for anabolic formation of tryptophan may have been constrained. It is suggested that 13C studies on appropriate fungi early in the idiophase of submerged or surface fermentation should be made before the biosynthesis of indole-diterpenoids can become clearer.
Keywords: Indole-diterpenes; Indole-3-glycerol phosphate; Secondary metabolism; Fermentation biochemistry; Alkaloids; Tryptophan; Nodulisporic acid A; Penitrem A; Lolitrem B; Roquefortine;
The potential role of green tea catechins in the prevention of the metabolic syndrome – A review by Frank Thielecke; Michael Boschmann (11-24).
Concepts to explain the protective effects of green tea catechins, particularly (−)-epigallocatechin-3-gallate (EGCG) the most abundant catechin, on parameters related to the metabolic syndrome (MetS) are available. An increasing number of human studies show potential benefits of green tea catechins on weight management, glucose control, and cardiovascular risk factors.The metabolic syndrome (MetS) represents an emerging health burden for governments and health care providers. Particularly relevant for prevention and early management of MetS are lifestyle conditions including physical activity and the diet. It has been shown that green tea, when consumed on a daily basis, supports health. Many of the beneficial effects of green tea are related to its catechin, particularly (−)-epigallocatechin-3-gallate (EGCG), content. There is conclusive evidence from in vitro and animal studies which provide the concepts for underlying functional mechanisms of green tea catechins and their biological actions. An increasing number of human studies have explored the effects of green tea catechins on the major MetS conditions such as obesity, type-2 diabetes and cardiovascular risk factors. This article provides a comprehensive overview of the human studies addressing the potential benefits of green tea catechins on the MetS.The number of human studies in this field is still limited. However, the majority of human epidemiological and intervention studies demonstrate beneficial effects of green tea or green tea extracts, rich in EGCG on weight management, glucose control and cardiovascular risk factors. The optimal dose has not yet been established.The current body of evidence in humans warrants further attention. In particular, well-controlled long-term human studies would help to fully understand the protective effects of green tea catechins on parameters related to the MetS.
Keywords: Green tea catechins; EGCG; Metabolic syndrome; Obesity; Diabetes; Cardiovascular health;
Insights into the catalytic properties of bamboo vacuolar invertase through mutational analysis of active site residues by Tai-Hung Chen; Yu-Chiao Huang; Chii-Shen Yang; Chien-Chih Yang; Ai-Yu Wang; Hsien-Yi Sung (25-31).
Invertase catalyzes the hydrolysis of sucrose to glucose and fructose. A theoretical structure of bamboo vacuolar invertase Boβfruct3 was constructed by homology modeling. The roles of amino acid residues that are conserved in or around the active site of the GH32 enzymes were studied by site-directed mutagenesis.Plant acid invertases, which are either associated with the cell wall or present in vacuoles, belong to family 32 of glycoside hydrolases (GH32). Homology modeling of bamboo vacuolar invertase Boβfruct3 using Arabidopsis cell-wall invertase AtcwINV1 as a template showed that its overall structure is similar to GH32 enzymes, and that the three highly conserved motifs, NDPNG, RDP and EC, are located in the active site. This study also used site-directed mutagenesis to examine the roles of the conserved amino acid residues in these three motifs, which include Asp135, Arg259, Asp260, Glu316 and Cys317, and a conserved Trp residue (Trp159) that resides between the NDPNG and RDP motifs. The mutants W159F, W159L, E316Q and C317A retained acid invertase activity, but no invertase activity was observed for the mutant E316A or mutants with changes at Asp135, Arg259, or Asp260. The apparent K m values of the four mutants with invertase activity were all higher than that of the wild-type enzyme. The mutants W159L and E316Q exhibited lower k cat values than the wild-type enzyme, but an increase in the k cat value was observed for the mutants W159F and C317A. The results of this study demonstrate that these residues have individual functions in catalyzing sucrose hydrolysis.
Keywords: Bambusa oldhamii; Poaceae; Bamboo; Homology modeling; Site-directed mutagenesis; Vacuolar invertase;
Two poplar methyl salicylate esterases display comparable biochemical properties but divergent expression patterns by Nan Zhao; Ju Guan; Farhad Forouhar; Timothy J. Tschaplinski; Zong-Ming Cheng; Liang Tong; Feng Chen (32-39).
Two methyl salicylate (MeSA) esterase (SABP2) genes, PtSABP2-1 and PtSABP2-2, were identified and cloned from poplar. The proteins encoded by PtSABP2-1 and PtSABP2-2 are 98% identical. Recombinant PtSABP2-1 and PtSABP2-2 displayed specific methyl esterase activity using MeSA as substrate to produce salicylic acid (SA). In addition to exhibiting comparable biochemical properties, PtSABP2-1 and PtSABP2-2 have conserved structural features. In contrast, PtSABP2-1 and PtSABP2-2 showed divergent expression patterns. The plausible evolutionary mechanisms leading to these two highly homologous MeSA esterase genes involved in divergent biological processes in poplar are discussed.Two genes encoding proteins of 98% sequence identity that are highly homologous to tobacco methyl salicylate (MeSA) esterase (SABP2) were identified and cloned from poplar. Proteins encoded by these two genes displayed specific esterase activities towards MeSA to produce salicylic acid, and are named PtSABP2-1 and PtSABP2-2, respectively. Recombinant PtSABP2-1 and PtSABP2-2 exhibited apparent Km values of 68.2 ± 3.8 μM and 24.6 ± 1 μM with MeSA, respectively. Structural modeling using the three-dimensional structure of tobacco SABP2 as a template indicated that the active sites of PtSABP2-1 and PtSABP2-2 were highly similar to that of tobacco SABP2. Under normal growing conditions, PtSABP2-1 showed the highest level of expression in leaves and PtSABP2-2 was most highly expressed in roots. In leaf tissues of poplar plants under stress conditions, the expression of PtSABP2-1 was significantly down-regulated by two stress factors, whereas the expression of PtSABP2-2 was significantly up-regulated by four stress factors. The plausible mechanisms leading to these two highly homologous MeSA esterase genes involved in divergent biological processes in poplar are discussed.
Keywords: Black cottonwood; Populus trichocarpa; Methyl esterase; SABP2; Methyl salicylate; Salicylic acid; Gene family; Molecular modeling;
Physcomitrella patens has lipoxygenases for both eicosanoid and octadecanoid pathways by Aldwin Anterola; Cornelia Göbel; Ellen Hornung; George Sellhorn; Ivo Feussner; Howard Grimes (40-52).
Two lipoxygenases from Physcomitrella patens use arachidonic acid preferentially as substrate to produce (12S)-HPETE, while five others preferentially use α-linolenic acid to produce (13S)-HPOTE.Mosses have substantial amounts of long chain C20 polyunsaturated fatty acids, such as arachidonic and eicosapentaenoic acid, in addition to the shorter chain C18 α-linolenic and linoleic acids, which are typical substrates of lipoxygenases in flowering plants. To identify the fatty acid substrates used by moss lipoxygenases, eight lipoxygenase genes from Physcomitrella patens were heterologously expressed in Escherichia coli, and then analyzed for lipoxygenase activity using linoleic, α-linolenic and arachidonic acids as substrates. Among the eight moss lipoxygenases, only seven were found to be enzymatically active in vitro, two of which selectively used arachidonic acid as the substrate, while the other five preferred α-linolenic acid. Based on enzyme assays using a Clark-type oxygen electrode, all of the active lipoxygenases had an optimum pH at 7.0, except for one with highest activity at pH 5.0. HPLC analyses indicated that the two arachidonic acid lipoxygenases form (12S)-hydroperoxy eicosatetraenoic acid as the main product, while the other five lipoxygenases produce mainly (13S)-hydroperoxy octadecatrienoic acid from α-linolenic acid. These results suggest that mosses may have both C20 and C18 based oxylipin pathways.
Keywords: Physcomitrella patens; Funariaceae; Lipoxygenase; Dioxygenase; Lipid peroxidation; Oxylipin formation; pH dependent positional specificity; Substrate orientation; Eicosanoid;
Arabidopsis 3-hydroxy-3-methylglutaryl-CoA reductase is regulated at the post-translational level in response to alterations of the sphingolipid and the sterol biosynthetic pathways by Benjamín Nieto; Oriol Forés; Montserrat Arró; Albert Ferrer (53-59).
3-Hydroxy-3-methylglutaryl-CoA reductase (HMGR) catalyzes the major rate-limiting step in the mevalonate pathway for sterol biosynthesis. In this study we report that regulation of HMGR activity in response to alterations of the sphingolipid and the sterol biosynthetic pathways in Arabidopsis thaliana is exerted at the post-translational level.3-Hydroxy-3-methylglutaryl-CoA reductase (HMGR, EC 184.108.40.206) catalyzes the major rate-limiting step in the mevalonate (MVA) pathway for isoprenoid biosynthesis. Its activity is regulated at different levels, from transcriptional to post-translational. Treatment of Arabidopsis thaliana plants with myriocin, a specific inhibitor of serine palmitoyltransferase (SPT), the first enzyme of sphingolipid biosynthesis, resulted in a concomitant reduction of both HMGR activity and the sterol content, which reveals regulatory cross-talk between these two lipid biosynthesis pathways. Myriocin-induced down-regulation of HMGR activity is exerted at the post-translational level, like the regulatory response of HMGR to enhancement or depletion of the flux through the sterol pathway.
Keywords: Arabidopsis thaliana; Regulation of plant metabolism; Isoprenoids; Mevalonate; Myriocin; Sphingolipids; 3-Hydroxy-3-methylglutaryl-CoA reductase (HMGR);
Xanthone biosynthesis in Hypericum perforatum cells provides antioxidant and antimicrobial protection upon biotic stress by Gregory Franklin; Luis F.R. Conceição; Erich Kombrink; Alberto C.P. Dias (60-68).
Xanthones are one of the most important classes of plant secondary metabolites commonly found in Hypericum and other Cluciaceae members. Here, we show that the coordinated functions of xanthones protect the plant cells from oxidative damage and help them to impair the pathogen growth upon biotic stress.Xanthone production in Hypericum perforatum (HP) suspension cultures in response to elicitation by Agrobacterium tumefaciens co-cultivation has been studied. RNA blot analyses of HP cells co-cultivated with A. tumefaciens have shown a rapid up-regulation of genes encoding important enzymes of the general phenylpropanoid pathway (PAL, phenylalanine ammonia lyase and 4CL, 4-coumarate:CoA ligase) and xanthone biosynthesis (BPS, benzophenone synthase). Analyses of HPLC chromatograms of methanolic extracts of control and elicited cells (HP cells that were co-cultivated for 24 h with A. tumefaciens) have revealed a 12-fold increase in total xanthone concentration and also the emergence of many xanthones after elicitation. Methanolic extract of elicited cells exhibited significantly higher antioxidant and antimicrobial competence than the equivalent extract of control HP cells indicating that these properties have been significantly increased in HP cells after elicitation. Four major de novo synthesized xanthones have been identified as 1,3,6,7-tetrahydroxy-8-prenyl xanthone, 1,3,6,7-tetrahydroxy-2-prenyl xanthone, 1,3,7-trihydroxy-6-methoxy-8-prenyl xanthone and paxanthone. Antioxidant and antimicrobial characterization of these de novo xanthones have revealed that xanthones play dual function in plant cells during biotic stress: (1) as antioxidants to protect the cells from oxidative damage and (2) as phytoalexins to impair the pathogen growth.
Keywords: Agrobacterium; Hypericum perforatum; Biotic stress; Xanthones; Antioxidant defense response; Elicitation; Phytoalexins;
Phytotoxicity of constituents of glandular trichomes and the leaf surface of camphorweed, Heterotheca subaxillaris by Masanori Morimoto; Charles L. Cantrell; Lynn Libous-Bailey; Stephen O. Duke (69-74).
Borneol (1), phytotoxic calamenene-type sesquiterpenes (2–5, 9–11) and methylated flavones (12–15) were isolated from the dichloromethane rinsate of camphorweed aerial tissues. The strongest plant growth inhibitor against Agrostis stolonifera and Lactuca sativa seedlings, as wells as duckweed (Lemna pausicostata), was 2-methoxy-calamenene-14-carboxylic acid (2).Camphorweed, Heterotheca subaxillaris (Lam.) Britt. & Rusby, has a camphor-like odor, and its leaf surfaces contain glandular trichomes of the type shown to contain high levels of isoprenoids in other species. Borneol (1), the phytotoxic calamenene-type sesquiterpenes (2–5, 9–11), and methylated flavones (12–15) were isolated from the dichloromethane rinsate of camphorweed aerial tissues. The strongest plant growth inhibitor against Agrostis stolonifera and Lactuca sativa seedlings, as well as duckweed (Lemna pausicostata), was 2-methoxy-calamenene-14-carboxylic acid (2). Esterification of calamenene carboxylic acids decreased their biological activity.
Keywords: Heterotheca subaxillaris; Asteraceae; Calamenene sesquiterpenes; Exudates; Phytotoxicity;
Antiplasmodial benzophenones from the trunk latex of Moronobea coccinea (Clusiaceae) by Guillaume Marti; Véronique Eparvier; Christian Moretti; Sophie Susplugas; Soizic Prado; Philippe Grellier; Pascal Retailleau; Françoise Guéritte; Marc Litaudon (75-85).
Phytochemical investigations of Moronobea coccinea (Clusiaceae) led to the isolation of 11 polycyclic polyprenylated acylphloroglucinol derivatives (3–8, 10–14) along with garcinol, isogarcinol and cycloxanthochymol. In vitro antiplasmodial assays reveal potent antimalarial activity for eight of them.In an effort to find antimalarial drugs, a systematic in vitro evaluation on a chloroquine-resistant strain of Plasmodium falciparum (FcB1) was undertaken on sixty plant extracts collected in French Guiana. The methanol extract obtained from the latex of Moronobea coccinea exhibited a strong antiplasmodial activity (95% at 10 μg/ml). The phytochemical investigation of this extract led to the isolation of eleven polycyclic polyprenylated acylphloroglucinols (PPAPs), from which eight showed potent antiplasmodial activity with IC50 ranged from 3.3 μM to 37.2 μM.
Keywords: Moronobea coccinea; Clusiaceae; Benzophenone; Coccinone; Antiplasmodial;
Polyphenols isolated from antiradical extracts of Mallotus metcalfianus by Céline Rivière; Van Nguyen Thi Hong; Luc Pieters; Bieke Dejaegher; Yvan Vander Heyden; Minh Chau Van; Joëlle Quetin-Leclercq (86-94).
A phytochemical investigation of Mallotus metcalfianus Croizat afforded 16 compounds including two new flavones: luteolin-7-O-(4″-O-(E)-coumaroyl)-β-glucopyranoside) (1), chrysoeriol-7-O-(4″-O-(E)-coumaroyl)-β-glucopyranoside) (2) and a mixture of two pairs of diastereoisomeric flavonolignans, (±)-hydnocarpin 7-O-(4″-O-(E)-coumaroyl)-β-glucopyranoside) ((±)-3a)/(±)-hydnocarpin-D 7-O-(4″-O-(E)-coumaroyl)-β-glucopyranoside) ((±)-3b) with a 2:1 ratio.Six flavonoids including two new flavones, luteolin 7-O-(4″-O-(E)-coumaroyl)-β-glucopyranoside), chrysoeriol-7-O-(4″-O-(E)-coumaroyl)-β-glucopyranoside) and a mixture of two pairs of diastereoisomeric flavonolignans, (±)-hydnocarpin 7-O-(4″-O-(E)-coumaroyl)-β-glucopyranoside)/(±)-hydnocarpin-D 7-O-(4″-O-(E)-coumaroyl)-β-glucopyranoside) with a 2:1 ratio were isolated from the whole plant of Mallotus metcalfianus Croizat, in addition to 10 known compounds. Their structures were evaluated on the basis of different spectroscopic methods, including extensive 1D and 2D NMR spectroscopy. Some extracts have moderate antimicrobial properties and interesting antiradical (DPPH) activity, as well as some compounds isolated from this species. Tannins were also identified in some active extracts.
Keywords: Mallotus metcalfianus Croizat; Euphorbiaceae; Flavones; Flavonolignans; Antiradical activities;
Cytotoxic benzil and coumestan derivatives from Tephrosia calophylla by Seru Ganapaty; Guttula Veera Kantha Srilakshmi; Steve Thomas Pannakal; Hafizur Rahman; Hartmut Laatsch; Reto Brun (95-99).
A benzil, calophione A, 1-(6′-Hydroxy-1′,3′-benzodioxol-5′-yl)-2-(6″-hydroxy-2″-isopropenyl-2″,3″-dihydro-benzofuran-5″-yl)-ethane-1,2-dione and three coumestan derivatives, tephcalostan B, C and D were isolated from the roots of Tephrosia calophylla. Compounds were evaluated for cytotoxicity against RAW (mouse macrophage cells) and HT-29 (colon cancer cells) cancer cell lines and antiprotozoal activity against various parasitic protozoa. Calophione A exhibited significant cytotoxicity with IC50 of 5.00 (RAW) and 2.90 μM (HT-29), respectively.A benzil, calophione A, 1-(6′-Hydroxy-1′,3′-benzodioxol-5′-yl)-2-(6″-hydroxy-2″-isopropenyl-2″,3″-dihydro-benzofuran-5″-yl)-ethane-1,2-dione and three coumestan derivatives, tephcalostan B, C and D were isolated from the roots of Tephrosia calophylla. Their structures were deduced from spectroscopic data, including 2D NMR 1H–1H COSY and 13C–1H COSY experiments. Compounds were evaluated for cytotoxicity against RAW (mouse macrophage cells) and HT-29 (colon cancer cells) cancer cell lines and antiprotozoal activity against various parasitic protozoa. Calophione A exhibited significant cytotoxicity with IC50 of 5.00 (RAW) and 2.90 μM (HT-29), respectively.
Keywords: Tephrosia calophylla; Fabaceae; Bioactive products; Benzil; Coumestan derivatives; Cytotoxicity; Antiprotozoal activity;
Azetidine-2-carboxylic acid in the food chain by Edward Rubenstein; Theresa McLaughlin; Richard C. Winant; Agustin Sanchez; Michael Eckart; Karolina M. Krasinska; Allis Chien (100-104).
Azetidine-2-carboxylic acid (Aze) 1 is a toxic and teratogenic non-protein amino acid found in roots of sugar beets and table beets. Aze 1 is misincorporated into proteins in place of proline 2 in numerous species, including human. Herein, we report the presence of Aze 1 in three sugar beet byproducts fed to livestock: shredded sugar beet pulp, pelleted sugar beet pulp, and sugar beet molasses.Azetidine-2-carboxylic acid (Aze) 1 is a non-protein amino acid present in sugar beets and in table beets (Beta vulgaris). It is readily misincorporated into proteins in place of proline 2 in many species, including humans, and causes numerous toxic effects as well as congenital malformations. Its role in the pathogenesis of disease in humans has remained unexplored. Sugar beet agriculture, especially in the Northern Hemisphere, has become widespread during the past 150 years, and now accounts for nearly 30% of the world’s supply of sucrose. Sugar beet byproducts are also used as a dietary supplement for livestock. Therefore, this study was undertaken as an initial survey to identify Aze-containing links in the food chain. Herein, we report the presence of Aze 1 in three sugar beet byproducts that are fed to farm animals: sugar beet molasses, shredded sugar beet pulp, and pelleted sugar beet pulp.
Keywords: Sugar beet; Beta vulgaris; Chenopodiaceae; Azetidine-2-carboxylic acid (Aze); Multiple sclerosis; p53;
Steroidal saponins from the roots of Trillium erectum (Beth root) by Patricia Y. Hayes; Reg Lehmann; Kerry Penman; William Kitching; James J. De Voss (105-113).
Eleven steroidal saponins including three saponins, two ecdysteroids and one fatty acid, have been isolated from the roots of Trillium erectum by RP-HPLC and characterized by spectroscopic (1D and 2D NMR) and spectrometric (LCMS) methods.Eleven steroidal saponins including three previously unreported saponins 1–3, two known ecdysteroids and one fatty acid, have been isolated from the roots of Trillium erectum (Beth root) by RP-HPLC and characterized by spectroscopic (1D and 2D NMR experiments) and spectrometric (LCMS) methods.
Keywords: Bethosides; Steroidal saponins; Trillium erectum; Beth root; Melanthiaceae; NMR; HPLC;
Dibenzocyclooctadiene lignans from Kadsura philippinensis by Ya-Ching Shen; Yu-Chi Lin; Yuan-Bin Cheng; Michael Y. Chiang; Shorong-Shii Liou; Ashraf Taha Khalil (114-120).
Dibenzocyclooctadiene lignans, kadsuphilols I–M, were isolated from aerial parts of Kadsura philippinensis (Schisandraceae).Lignans with the dibenzocyclooctadiene skeleton, kadsuphilols I–L, and one C19-homolignan, kadsuphilol M, were isolated by chromatographic fractionation of an ethyl acetate extract of the aerial parts of Kadsura philippinensis. Their structures were elucidated through extensive spectroscopic methods, including HRESIMS and 2D NMR experiments (HMQC, COSY and HMBC). The stereochemistry at the chiral centers and the biphenyl moist, were determined using NOESY, as well as analysis of CD spectra, respectively. The relative configuration of heteroclitin J was confirmed by single crystal X-ray crystallographic analysis. The in vitro radical-scavenging activities of these compounds by using DPPH were evaluated.
Keywords: Kadsura philippinensis; Schisandraceae; Lignans; Dibenzocyclooctadiene; Homolignans; Antioxidative activity;
Metabolites from the endophytic mitosporic Dothideomycete sp. LRUB20 by Porntep Chomcheon; Suthep Wiyakrutta; Nongluksna Sriubolmas; Nattaya Ngamrojanavanich; Chulabhorn Mahidol; Somsak Ruchirawat; Prasat Kittakoop (121-127).
Dothideopyrones A–D (1, 3, 4, and 5), together with seven known compounds were isolated from the endophytic mitosporic Dothideomycete sp., and cis, trans-muconic acid was isolated as a natural product for the first time.The endophytic mitosporic Dothideomycete sp. LRUB20 was found to produce pyrone derivatives, dothideopyrones A–D (1, 3, 4, and 5), together with seven known compounds, including questin (9), asterric acid (10), methyl asterrate (11), sulochrin (12), and eugenitin (13), 6-hydroxymethyleugenitin (14), and cis, trans-muconic acid (15). Dothideopyrone D (5) and its acetate derivative 6 exhibited moderate cytotoxic activity. This is the first report on a naturally occurring muconic acid, which is commonly known as a biomarker in environments after exposure to benzene and phenol (or derivatives). Interestingly, the LRUB20 fungus could produce muconic acid in relatively high yield (47.8 mg/L). The utility of endophytic fungi in the field of white biotechnology is discussed.
Keywords: Dothideomycete sp.; Endophytic fungi; Pyrone; Muconic acid; Bioactive compounds; Cytotoxic activity; White biotechnology; Building blocks;
Aspernolides A and B, butenolides from a marine-derived fungus Aspergillus terreus by Rajesh R. Parvatkar; Celina D’Souza; Ashootosh Tripathi; Chandrakant G. Naik (128-132).
Two derivatives, Aspernolides A (1) and B (2) of a well known CDK inhibitor, butyrolactone I (3) were isolated from the culture medium of a marine derived fungus Aspergillus terreus.Two aromatic butenolides, aspernolides A and B along with the known metabolites, butyrolactone I, terrein and physcion were isolated from the fermentation broth of a soft coral derived fungus Aspergillus terreus. The structures of these metabolites were assigned on the basis of detailed spectroscopic analysis. The absolute stereochemistry of aspernolides A (1) and B (2) was established by their preparation from the known butyrolactone I. Biogenetically aspernolides A and B must be derived from butyrolactone I, a well known specific inhibitor of cyclin dependent kinase (cdk) from A. terreus. When tested, aspernolide A exhibited mild cytotoxicity against cancer cell lines.
Keywords: Aspergillus terreus; Marine natural products; Butenolides; Butyrolactone I; Aspernolides;
Kuguacins F–S, cucurbitane triterpenoids from Momordica charantia by Jian-Chao Chen; Wu-Qing Liu; Lu Lu; Ming-Hua Qiu; Yong-Tang Zheng; Liu-Meng Yang; Xian-Min Zhang; Lin Zhou; Zhong-Rong Li (133-140).
Fourteen cucurbitane derivatives, including two pentanorcucurbitacins, one octanorcucurbitacin, and two trinorcucurbitacins, were isolated from the vines and leaves of Momordica charantia.Chemical investigation of the vines and leaves of Momordica charantia resulted in isolation of fourteen cucurbitane triterpenoids, kuguacins F–S (1–14), including two pentanorcucurbitacins (6 and 7), one octanorcucurbitacin (8), and two trinorcucurbitacins (11 and 12), along with six known analogues. Their structures were elucidated on the basis of extensive spectroscopic and single-crystal X-ray diffraction analyses. Compounds 1–14 exhibited weak anti-HIV-1 activities in vitro.
Keywords: Momordica charantia; Cucurbitaceae; Cucurbitane triterpenoids; Kuguacins F–S;
Chromone and chromanone glucosides from Hypericum sikokumontanum and their anti-Helicobacter pylori activities by Naonobu Tanaka; Yoshiki Kashiwada; Tatsuro Nakano; Hirofumi Shibata; Tomihiko Higuchi; Michiko Sekiya; Yasumasa Ikeshiro; Yoshihisa Takaishi (141-146).
Chromone glucosides, takanechromones A–C (1, 2 and 5) and chromanone glucosides, takanechromanones A and B (3 and 4) were isolated from the methanolic extracts of Hypericum shikokumontanum together with 27 known compounds. Their structures were established based on spectroscopic evidence. The isolated compounds and some chromone derivatives were assayed for antimicrobial activity against Helicobacter pylori and cytotoxicity against human cancer cell lines. Anti-H. pylori activity was observed in 5,7-dihydroxy-3-methylchromone (6) and 3-ethyl-5-methoxy-7-hydroxychromone (7a), while 6 and 5,7-dihydroxy-3-ethylchromone (7) showed cytotoxicities against multi-drug resistant cancer cell lines comparable to those of doxorubicin.Chromone glucosides, takanechromones A–C (1, 2 and 5) and chromanone glucosides, named takanechromanones A and B (3 and 4), were isolated from the methanolic extracts of Hypericum sikokumontanum together with 27 known compounds. Their structures were established based on spectroscopic evidence. The isolated compounds and some chromone derivatives were assayed for antimicrobial activity against Helicobacter pylori and cytotoxicity against human cancer cell lines.
Keywords: Hypericum sikokumontanum; Guttiferae; Chromone glucoside; Chromanone glucoside; Helicobacter pylori; Cytotoxicity;
On the role of the monolignol γ-carbon functionality in lignin biopolymerization by Anders Holmgren; Magnus Norgren; Liming Zhang; Gunnar Henriksson (147-155).
Dehydrogenation polymers were generated through enzymatic oxidation of ferulic acid, coniferaldehyde and coniferyl alcohol, respectively. Chemical and physical properties of the materials were determined in order to discuss why plants prefer the alcohol for lignin biosynthesis and not the acid and aldehyde, which are biologically cheaper to produce.In order to investigate the importance of the monomeric γ-carbon chemistry in lignin biopolymerization and structure, synthetic lignins (dehydrogenation polymers; DHP) were made from monomers with different degrees of oxidation at the γ-carbon, i.e., carboxylic acid, aldehyde and alcohol. All monomers formed a polymeric material through enzymatic oxidation. The polymers displayed similar sizes by size exclusion chromatography analyses, but also exhibited some physical and chemical differences. The DHP made of coniferaldehyde had poorer solubility properties than the other DHPs, and through contact angle of water measurement on spin-coated surfaces of the polymeric materials, the DHPs made of coniferaldehyde and carboxylic ferulic acid exhibited higher hydrophobicity than the coniferyl alcohol DHP. A structural characterization with 13C NMR revealed major differences between the coniferyl alcohol-based polymer and the coniferaldehyde/ferulic acid polymers, such as the predominance of aliphatic double bonds and the lack of certain benzylic structures in the latter cases. The biological role of the reduction at the γ-carbon during monolignol biosynthesis with regard to lignin polymerization is discussed.
Keywords: Lignin; Monolignol biosynthesis; Lignin-polysaccharide networks; Plant cell wall; Biopolymer;
Retraction notice to 7,8-benzoflavone: a phytotoxin from root exudates of invasive Russian knapweed [Phytochemistry 64 (2003) 493–497] by Frank R. Stermitz; Harsh P. Bais; Tommaso A. Foderaro; Jorge M. Vivanco (156).