Cryptoporic acids A-G, drimane-type sesquiterpenoid ethers of isocitric acid from the fungus Cryptoporus volvatus

Abstract

Seven novel bitter drimane-type sesquiterpenoids with an isocitric acid group named cryptoporic acids (CA) A-G have been isolated from the fungus Cryptoporous volvatus and their absolute stereostructures established by a combination of chemical transformation, NMR spectral data and X-ray crystallographic analysis. Cryptoporic acids strongly inhibited the release of superoxide anion radicals from guinea-pig peritoneal macrophage as well as rabbit polymorphonuclear leucocyte. CA-E showed anti-tumour promoting activity whilst CA-D slightly enhanced tumour promoting and protein kinase C activity. CAs also inhibited elongation of the second coleoptile and germination of rice in husk at 200 ppm. © 1992.