Azacoccones A − E, five new aza-epicoccone derivatives from Aspergillus flavipes

Abstract Azacoccones A–E ( 1 – 5 ), five new aza-epicoccone derivatives, were isolated from the culture of Aspergillus flavipes . Their structures were determined by extensive NMR spectroscopic analyses and the absolute configuration of 5 was determined by electronic circular dichroism (ECD) calculation. Compounds 1 – 5 are proposed to be generated via a Pictet-Spengler reaction-based biosynthetic route starting from the precursor flavipin. Pictet–Spengler reaction is rarely found in the fungal kingdom, which indicated the distinctive nature of 1 – 5 . Compounds 3 and 5 exhibit significant free radical scavenging activities with IC 50 values of 4.0 and 2.4 μg/mL, respectively, which are better than the positive control trolox (4.55 μg/mL).