Chuan-Xi Wang

Antioxidative Phenylpropanoid-Substituted Epicatechin Glycosides from Parabarium huaitingii

Three new phenylpropanoid-substituted epicatechin glycosides, namely parabarosides A - C ( 1- 3), together with three known compounds, 5-caffeoylquinic acid (4), 5-caffeoylshikimic acid (5), and 3,4-dicaffeoylquinic acid (6), were obtained from the plant Parabarium huaitingii. Their structures were determined and full assignments of (1)H- and (13)C-NMR spectroscopic data were achieved by analyses of 1D- and 2D-NMR, mass, and CD spectra. The oxygen radical absorbance capacity (ORAC) assay was applied to evaluate their antioxidative capacity in vitro, which revealed that 1- 6 showed strong antioxidative properties.

New oxidized sterols from Aspergillus awamori and the endo-boat conformation adopted by the cyclohexene oxide system.

Two new oxidized sterols 1 and 2 were obtained from the active fraction of a mangrove fungus Aspergillus awamori isolated from the soils around the mangrove plant Acrostichum speciosum. Their structures were elucidated using spectroscopic methods as 22E‐7α‐methoxy‐5α,6α‐epoxyergosta‐8(14),22‐dien‐3β‐ol (1) and 22E‐3β‐hydroxy‐5α,6α,8α,14α‐diepoxyergosta‐22‐en‐7‐one (2). The NMR data and complete assignments for both DMSO‐d6 and CDCl3 were given. Their cytotoxic activity against A549 cell line was evaluated. Furthermore, the detailed conformation analysis for ring B (cyclohexene oxide system) of sterol 1 was given on the basis of NOEs. The endo‐boat conformation was considered as the preferred conformation for ring B rather than half‐chair conformation. Copyright

Talaflavuterpenoid A, a new nardosinane-type sesquiterpene from Talaromyces flavus

Talaflavuterpenoid A (1), a new nardosinane-type sesquiterpene, was isolated from the wetland soil-derived fungus Talaromyces flavus BYD07-13, and its structure was elucidated on the basis of HR-MS, NMR, and X-ray diffraction analysis. The absolute configuration of 1 was established by comparing the experimental electronic circular dichroism (ECD) spectrum with the calculated ECD spectra. Its cytotoxic effects on five human tumor cell lines (HL-60, SMMC-7721, A-549, MCF-7, and SW480), and antimicrobial activity against Escherichia coli, Staphylococcus aureus, Candida albicans, and Aspergillus niger were evaluated. This is the first report of the presence of nardosinane-type sesquiterpene in Talaromyces sp.

4,5-seco-Probotryenols A–C, a new type of sesquiterpenoids from Stachybotrys bisbyi

4,5-seco-Probotryenols A–C (1–3), a new type of sesquiterpenoids named seco-probotryane-type sesquiterpenoid, have been obtained from Stachybotrys bisbyi (PYH05-7), along with five new botryane skeleton sesquiterpenoids (4, 5, and 8–10), and two known ones (6 and 7). Their structures were determined by NMR analyses, chemical derivatization, and X-ray crystallography.

Adeninealkylresorcinol, the first alkylresorcinol tethered with nucleobase from Lasiodiplodia sp.

Adeninealkylresorcinol (1), an unusual alkylresorcinol with adenine-alkylresorcinol conjoined skeleton, was isolated from an endophytic fungus Lasiodiplodia sp. obtained from a traditional Chinese medicine Houttuynia cordata Thunb., together with three new biogenetically related compounds (2-4). Their structures were elucidated by comprehensive spectroscopic analysis, and the absolute configuration of 4 was determined by the modified Moshers method and quantum chemical calculation. Among them, adeninealkylresorcinol (1) is the first alkylresorcinol tethered with nucleobase. In addition, the antioxidant, cytotoxic, and antimicrobial activities of 1-3 were evaluated.

Pericoterpenoid A, a new bioactive cadinane-type sesquiterpene from Periconia sp.

Pericoterpenoid A (1), a new cadinane-type sesquiterpene, was isolated from an endolichenic fungal strain Periconia sp. (No. 19-4-2-1). Its structure was characterized by analyzing the spectroscopic data (IR, MS, 1D- and 2D-NMR). The antimicrobial activity against Escherichia coli, Staphylococcus aureus, Aspergillus niger, and Candida albicans was evaluated. Pericoterpenoid A showed moderate antimicrobial activity against A. niger and weak activity against C. albicans. This is the first report of the presence of cadinane-type sesquiterpene in Periconia sp.

New phenethylamine derivatives from Arenibacter nanhaiticus sp. nov. NH36A(T) and their antimicrobial activity.

Five new phenethylamine (PEA) derivatives (1–5) were isolated from the strain of Arenibacter nanhaiticus sp. nov. NH36AT derived from the marine sediment of the South China Sea by bioassay-guided fractionation. Their structures were elucidated by spectroscopic methods including UV, IR, HR-MS and NMR. Interestingly, compounds 1–4 existed as enantiomers, which were resolved by chiral liquid chromatography. The resolved configuration of each enantiomer was assigned by the Marfey’s method. Of these compounds, 5 showed weak antimicrobial activity against Staphylococcus aureus and Bacillus subtilis with MIC values of 0.50 and 0.25 mg ml−1, respectively.

Biosynthesis of helvolic acid and identification of an unusual C-4-demethylation process distinct from sterol biosynthesis

Fusidane-type antibiotics represented by helvolic acid, fusidic acid and cephalosporin P1 are a class of bacteriostatic agents, which have drawn renewed attention because they have no cross-resistance to commonly used antibiotics. However, their biosynthesis is poorly understood. Here, we perform a stepwise introduction of the nine genes from the proposed gene cluster for helvolic acid into Aspergillus oryzae NSAR1, which enables us to isolate helvolic acid (~20 mg L−1) and its 21 derivatives. Anti-Staphylococcus aureus assay reveals that the antibacterial activity of three intermediates is even stronger than that of helvolic acid. Notably, we observe an unusual C-4 demethylation process mediated by a promiscuous short-chain dehydrogenase/reductase (HelC) and a cytochrome P450 enzyme (HelB1), which is distinct from the common sterol biosynthesis. These studies have set the stage for using biosynthetic approaches to expand chemical diversity of fusidane-type antibiotics.The biosynthetic pathway of fusidane-type antibiotics, such as helvolic acid, is largely undiscovered. Here, the authors investigate the biosynthesis of helvolic acid, thereby determining the sequence of the enzymatic reactions involved in the process and the intermediates formed.

Three Pairs of New Isopentenyl Dibenzo[b,e]oxepinone Enantiomers from Talaromyces flavus, a Wetland Soil-Derived Fungus

Three pairs of new isopentenyl dibenzo[b,e]oxepinone enantiomers, (+)-(5S)-arugosin K (1a), (−)-(5R)-arugosin K (1b), (+)-(5S)-arugosin L (2a), (−)-(5R)-arugosin L (2b), (+)-(5S)-arugosin M (3a), (−)-(5R)-arugosin M (3b), and a new isopentenyl dibenzo[b,e]oxepinone, arugosin N (4), were isolated from a wetland soil-derived fungus Talaromyces flavus, along with two known biosynthetically-related compounds 5 and 6. Among them, arugosin N (4) and 1,6,10-trihydroxy-8-methyl-2-(3-methyl-2-butenyl)-dibenz[b,e]oxepin-11(6H)-one (CAS: 160585-91-1, 5) were obtained as the tautomeric mixtures. The structures of isolated compounds were determined by detailed spectroscopic analysis. In addition, the absolute configurations of these three pairs of new enantiomers were determined by quantum chemical ECD calculations.

A Single Gene Cluster for Chalcomycins and Aldgamycins: Genetic Basis for Bifurcation of Their Biosynthesis

Aldgamycins are 16‐membered macrolide antibiotics with a rare branched‐chain sugar d‐aldgarose or decarboxylated d‐aldgarose at C‐5. In our efforts to clone the gene cluster for aldgamycins from a marine‐derived Streptomyces sp. HK‐2006‐1 capable of producing both aldgamycins and chalcomycins, we found that both are biosynthesized from a single gene cluster. Whole‐genome sequencing combined with gene disruption established the entire gene cluster of aldgamycins: nine new genes are incorporated with the previously identified chalcomycin gene cluster. Functional analysis of these genes revealed that almDI/almDII, (encoding α/β subunits of pyruvate dehydrogenase) triggers the biosynthesis of aldgamycins, whereas almCI (encoding an oxidoreductase) initiates chalcomycins biosynthesis. This is the first report that aldgamycins and chalcomycins are derived from a single gene cluster and of the genetic basis for bifurcation in their biosynthesis.