Three new metabolites, furobenzotropolones A, B (1-2) with unusual benzene and dihydrofuran moieties and 3-hydroxyepicoccone B (3), together with seven known compounds (4-10) were obtained from the endophytic fungus Epicoccum nigrum MLY-3 isolated from the fresh leaf of mangrove plant Bruguiear gymnorrhiza collected from Zhuhai. Their structures were assigned by the analysis of UV, IR, NMR, and mass spectroscopic data. Compound 1 was further confirmed by single-crystal X-ray diffraction experiment using Cu Kα radiation. In antioxidant activities in vitro, compounds 2, 3, 5, and 8 showed promising DPPH· scavenging activity with IC50 values ranging from 14.7 to 29.3 µM. Compounds 2, 3, 5, 7, and 8 exhibited promising potent activity in scavenging ABTS· with IC50 values in the range of 18-29.2 µM, which was stronger than that of the positive control ascorbic acid (IC50 = 33.6 ± 0.8 µM).
Keywords: ABTS· scavenging activity; DPPH· scavenging activity; Epicoccum nigrum; furobenzotropolone; mangrove endophytic fungus.