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

Three new dibenzo- α -pyrone derivatives, alternolides A-C ( 1 - 3 ), and seven known congeners ( 4 - 10 ) were isolated from the marine-derived fungus of Alternaria alternata LW37 assisted by the one strain-many compounds (OSMAC) strategy. The structures of 1 - 3 were established by extensive spectroscopic analyses, and their absolute configurations were determined by modified Snatzke's method and electronic circular dichroism (ECD) calculations. Compounds 6 and 7 showed good 1,1-diphenyl-2-picrylhydrazyl (DPPH) antioxidant scavenging activities with IC 50 values of 83.94 ± 4.14 and 23.60 ± 1.23 µM, respectively. Additionally, 2 , 3 and 7 exhibited inhibitory effects against α -glucosidase with IC 50 values of 725.85 ± 4.75, 451.25 ± 6.95 and 6.27 ± 0.68 µM, respectively. The enzyme kinetics study indicated 2 and 3 were mixed-type inhibitors of α -glucosidase with K i values of 347.0 and 108.5 µM, respectively. Furthermore, the interactions of 2 , 3 and 7 with α -glucosidase were investigated by molecular docking.