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.