Diaporthin

Five chromone derivatives, including 2,6-dimethyl-5-methoxyl-7-hydroxylchromone (1), 6-hydroxymethyleugenin (2), 6-methoxymethyleugenin (3), chaetoquadrin D (4), and isoeugenitol (5), and three isocoumarin congeners, namely diaporthin (6), 8-hydroxy-6-methoxy-3-methylisocoumarin (7), and 6-methoxymellein (8), were isolated from the culture of the endophytic fungus Xylomelasma sp. Samif07 derived from the medicinal plant Salvia miltiorrhiza Bunge. Among them, compound 1 was a new natural product. Their structures were determined by spectroscopic methods and comparison with the literature. The isolated compounds were evaluated for their antibacterial and antioxidant activities. Compound 5 showed notable antitubercular activity against Mycobacterium tuberculosis with MIC value of 10.31 µg/mL, while compounds 1-3, and 5-7 displayed inhibitory activities against the other bacteria with MIC range of 25 ~ 100 µg/mL. Meanwhile, compound 6 showed potent hydroxyl radical-scavenging activity with EC50 value of 15.1 µg/mL, while compounds 5-7 showed certain ferric reducing ability.

Two new polyketides, 8-O-methylnodulisporin F (1) and nodulisporin H (2), two new naphthoquinones, 5-hydroxy-2-methoxy-6,7-dimethyl-1,4-naphthoquinone (3) and 5-hydroxy-2-methoxynaphtho[9-c]furan-1,4-dione (4), and a new naphthofuran 1,3,8-trimethoxynaphtho[9-c]furan (5), along with five known compounds 4-O-methyl eleutherol (6), 2-acetyl-7-methoxybenzofuran (7), (-)-orthosporin (8), diaporthin (9), and 6-hydroxymellein (10), were obtained from the EtOAc extract of the mangrove-derived fungus Daldinia eschscholtzii HJ004. The structures of the isolated compounds were elucidated by extensive NMR and MS analyses, while the absolute configurations of the stereogenic carbons were established based on experimental and calculated electronic circular dichroism spectra. Compounds 4 and 7 displayed a potent inhibitory activity against α-glucosidase with the IC50 values of 5.7 and 1.1 μg/mL, respectively. Compounds 1 and 2 showed a moderate antibacterial activity against Staphylococcus aureus, methicillin-resistant S. aureus (MRSA) and Bacillus cereus, with minimum inhibitory concentration (MIC) values ranging from 6.25 to 12.5 μg/mL. Compound 3 exhibited antibacterial activity against B. cereus with the MIC value of 12.5 μg/mL.

From the deep-sea-derived Fusarium sp. ZEN-48, four known compounds were obtained. Their structures were established by extensive analyses of the NMR, HR-ESI-MS, and the X-ray crystallographic data as brefeldin A (BFA, 1), brevianamide F (2), N-acetyltryptamine (3), and (+)-diaporthin (4). Although BFA was extensively investigated for its potent bioactivities, its role on TNFα-induced necroptosis was incompletely understood. In this study, BFA showed significant inhibition on TNFα-induced necroptosis by disrupting the necrosome formation and suppressing the phosphorylation of RIPK3 and MLKL (IC50 =0.5 μM). While, it had no effect on TNFα-induced NF-κB/MAPKs activation and apoptosis. The finding raised significant implications of BFA for necroptosis-related inflammatory disease therapy and new drug development from marine fungi.