New Dibenzo- α -pyrone Derivatives with α -Glucosidase Inhibitory Activities from the Marine-Derived Fungus Alternaria alternata

Three new dibenzo- -pyrone derivatives, alternolides A-C ( - ), and seven known congeners ( - ) were isolated from the marine-derived fungus of LW37 assisted by the one strain-many compounds (OSMAC) strategy. The structures of - were established by extensive spectroscopic analyses, and their absolute configurations were determined by modified Snatzke's method and electronic circular dichroism (ECD) calculations. Compounds and showed good 1,1-diphenyl-2-picrylhydrazyl (DPPH) antioxidant scavenging activities with IC values of 83.94 ± 4.14 and 23.60 ± 1.23 µM, respectively. Additionally, , and exhibited inhibitory effects against -glucosidase with IC values of 725.85 ± 4.75, 451.25 ± 6.95 and 6.27 ± 0.68 µM, respectively. The enzyme kinetics study indicated and were mixed-type inhibitors of -glucosidase with values of 347.0 and 108.5 µM, respectively. Furthermore, the interactions of , and with -glucosidase were investigated by molecular docking.