Guo-Dong Chen

Xanthoquinodins from the endolichenic fungal strain Chaetomium elatum.

Five new xanthoquinodins, A4-A6 (1-3), B4 (4), and B5 (5), were isolated from the crude extract of the endolichenic fungal strain Chaetomium elatum (No. 63-10-3-1), along with three known xanthoquinodins, A1-A3 (6-8). Their structures were determined by detailed spectroscopic analysis and comparison of the NMR data with those of the closely related compounds previously reported. The absolute configuration of 1 was established by X-ray crystallographic analysis and ECD calculation. The cytotoxic activity of all compounds was tested against HL-60, SMMC-7721, A-549, MCF-7, and SW480 human cancer cell lines.

Nodulisporisteriods A and B, the first 3,4-seco-4-methyl-progesteroids from Nodulisporium sp.

Two new 4-methyl-progesteroids, nodulisporisteriod A (1) and nodulisporisteriod B (2), were isolated from the extract of an endolichenic fungal strain Nodulisporium sp. (No. 65-17-2-1), along with two related metabolites, demethoxyviridin (3) and inoterpene B (4). Their structures were determined by detailed spectroscopic analyses, X-ray crystallographic analysis and comparison of the NMR data with those of the closely related compounds previously reported. Nodulisporisteriod A (1) and nodulisporisteriod B (2) possess new carbon skeletons, which are the first cases of fission at C-3,4 in 4-methyl-progesteroids. A hypothetical biosynthetic pathway for 1 and 2 was proposed. Moreover, the Aβ42 aggregation inhibitory activities of 1-4 were evaluated using standard thioflavin T (ThT) fluorescence assay with epigallocatechin gallate (EGCG) as positive control. Demethoxyviridin (3) displayed anti-Aβ42 aggregation activity with IC50 value of 13.4μM.

(±)-Quassidines I and J, Two Pairs of Cytotoxic Bis-β-carboline Alkaloid Enantiomers from Picrasma quassioides

(±)-Quassidines I (1) and J (2), two pairs of new bis-β-carboline alkaloid enantiomers, were isolated from the stems of Picrasma quassioides. Their structures were determined by the analysis of spectroscopic data, including HRESIMS and 2D NMR, and confirmed by single-crystal X-ray diffraction analysis. The racemic mixtures of 1 and 2 were resolved into two pairs of enantiomers, (+)-S-1a and (-)-R-1b and (+)-S-2a and (-)-R-2b, by HPLC using a chiral Daicel IB-3 column, respectively, which represents the first successful example to resolve bis-β-carboline racemic mixtures. The absolute configurations of the two pairs of enantiomers were determined by comparison between the calculated and experimental ECD spectra. The cytotoxicity evaluation revealed that (+)-S-1a and (+)-S-2a showed more potent cytotoxicity against human cervical HeLa and gastric MKN-28 cancer cell lines with IC50 values of 4.03-6.30 μM than their enantiomers with IC50 values of 9.64-12.3 μM; however, the two (+)-S-quassidines showed similar activities to their enantiomers against the mouse melanoma B-16 cancer cell line.

Dysiherbols A-C and Dysideanone E, Cytotoxic and NF-κB Inhibitory Tetracyclic Meroterpenes from a Dysidea sp. Marine Sponge.

Four new tetracyclic meroterpnes, dysiherbols A-C (1-3) and dysideanone E (4), were isolated from a Dysidea sp. marine sponge collected from the South China Sea. Their complete structures and absolute configurations were unambiguously determined by a combination of NMR spectroscopic data, ECD calculations, and single-crystal X-ray diffraction analysis. Within the sesquiterpene quinol structures, dysiherbols A-C possess an intriguing 6/6/5/6-fused tetracyclic carbon skeleton. The NF-κB inhibitory and cytotoxic activity evaluation disclosed that dysiherbol A (1) showed potent activity with respective IC50 values of 0.49 and 0.58 μM, which were about 10-fold and 20-fold more potent than those of dysiherbols B (2) and C (3), which feature hydroxy and ketone carbonyl groups at the C-3 position.

Two new naphthalene derivatives from an endolichenic fungal strain Scopulariopsis sp.

Chemical investigation on an endolichenic fungal strain Scopulariopsis sp. led to the isolation of two new naphthalene derivatives, 1-(4′-hydroxy-3′,5′-dimethoxy-phenyl)-1,8-dimethoxynaphthalen-2(1H)-one (1) and 1,8-dimethoxynaphthalen-2-ol (2). Their structures were determined by spectroscopic techniques (UV, IR, MS, 1D, and 2D NMR).

Nodulisporiviridins A-H, Bioactive Viridins from Nodulisporium sp.

Eight new viridins, nodulisporiviridins A-H (1-8), were isolated from the extract of an endolichenic fungal strain Nodulisporium sp. (No. 65-17-2-1) that was fermented with potato-dextrose broth. The structures were determined using spectroscopic and X-ray crystallographic analysis. Nodulisporiviridins A-D (1-4) are unique viridins with an opened ring A. The Aβ42 aggregation inhibitory activities of 1-8 were evaluated using a thioflavin T (ThT) assay with epigallocatechin gallate (EGCG) as the positive control (EGCG IC50 of 0.5 μM). Nodulisporiviridin G (7) displayed potent inhibitory activity with an IC50 value of 1.2 μM, and the preliminary trend of activity of these viridins as Aβ42 aggregation inhibitors was proposed. The short-term memory assay on an Aβ transgenic drosophila model of Alzheimers disease showed that all eight compounds improved the short-term memory capacity, with potencies close to that of the positive control (memantine).

Dimericbiscognienyne A: A Meroterpenoid Dimer from Biscogniauxia sp. with New Skeleton and Its Activity

Dimericbiscognienyne A (1), an unusual diisoprenyl-cyclohexene-type meroterpenoid dimer, was isolated from Biscogniauxia sp. together with three new monomeric diisoprenyl-cyclohexene-type meroterpenoids (2-4) and one new isoprenyl-benzoic acid-type meroterpenoid (5). All structures were determined by extensive NMR spectroscopic methods, quantum chemical calculations, chemical derivatization, and X-ray crystallography. The formation of 1 is related to a unique intermolecular redox coupling Diels-Alder adduct reaction. Their cytotoxicities and short-term memory enhancement activities against Alzheimers disease were assessed.

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

Stachybisbins A and B, the first cases of seco-bisabosquals from Stachybotrys bisbyi

Stachybisbins A (1) and B (2), two new meroterpenoids with unprecedented seco-bisabosqual skeleton, together with three biogenetically related metabolites (3-5), were isolated from a wetland fungal strain of Stachybotrys bisbyi. The structures of the new compounds were determined by spectroscopic analyses, modified Moshers method, and quantum chemical CD method. The cytotoxic activities of all compounds were tested against HL-60, SMMC-7721, A-549, MCF-7, and SW480 human cancer cell lines.

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.