Two new tetralones from the endophytic fungus Annulohypoxylon stygium A888

Two new tetralones, annulohyporins A (1) and B (2), along with thirteen known compounds (3–15), were isolated from the ethyl acetate extract of solid fermentation of the endophytic fungus Annulohypoxylon stygium A888, which was isolated from the medicinal plant Aquilaria sinensis. The structures of annulohyporins A and B were established by detailed analyses of ultraviolet-visible spectroscopy (UV), infrared spectroscopy (IR), mass spectrometry (MS), electronic circular dichroism (ECD) calculations and nuclear magnetic resonance (NMR). Bioactivity assay showed that compounds 3 and 4 had significant α-glucosidase inhibitory activities with IC50 values of 64.00 and 32.90 µM, respectively.