Structure and Insecticidal Activity of New Indole Alkaloids, Okaramines A and B, from Penicillium simplicissimum AK-40

Abstract

Penicillium simplicissimum AK-40, which was isolated from a soil sample, produced novel insecticidal compounds when cultured with okara (the insoluble residue of whole soybean). The metabolites, named okaramine A (1) and B(2), were crystalline products with molecular formulas C₃₂H₃₂N₄O₃ and C₃₃H₃₄N₄O₅, respectively. The structure of 1 was deduced from the structure of acetylokaramine A that was established by single crystal X-ray diffraction. The structure of 2 was determined from the data of UV, IR, NMR (¹H and ¹³C) and mass spectrometry. 1 and 2 showed insecticidal activity against the 3rd instar larvae of silkworm at doses of 3 μg/g of diet and 0.1 μg/g of diet, respectively.