Kipukasin and oxepinamide derivatives from an undescribed Aspergillus sp

In the course of our ongoing studies of fungicolous fungi, an isolate of Aspergillus sp. (MYC-2152=NRRL 62124) was obtained from a basidioma of an Inonotus sp. found on a dead soap berry tree in a forest in Kipuka ki (Volcanoes National Park) in the Ka'u District of Hawaii. Sequencing studies later showed that this isolate was a representative of an undescribed species of Aspergillus Section Versicolores (GenBank Accession No. JN093265). The ethyl acetate extract obtained from solid-substrate fermentation cultures of this isolate showed showed antifungal activity against Fusarium verticillioides and antiinsectan activity against Spodoptera frugiperda (fall armyworm). Chemical investigation of this extract afforded two new kipukasin derivatives (named kipukasins H and I) and a new stereoisomer of oxepinamide E. The structures of these compounds were assigned using various 1D and 2D NMR techniques, HRESIMS, and CD spectroscopy. Nine known compounds were also encountered (sterigmatocystin, stephacidin A, 6,8-di-O-methylnidurufin, avrainvillamide, aspergamide A, and notoamides D, E, F, and K). The majority of the activity observed for the extract can be accounted for by high levels of sterigmatocystin, although the new oxepinamide E analogue also showed antiinsectan effects.