New metabolic products of Aspergillus flavus. Part IV. 4′-Hydroxyasperentin and 5′-hydroxyasperentin 8-methyl ether

Abstract

A previously isolated minor metabolic product of an entomogenous strain of Aspergillus flavus is shown to be a 4′-hydroxyasperentin [3,4-dihydro-6,8-dihydroxy-3-(4-hydroxy-6-methyltetrahydropyran-2-ylmethyl)isocoumarin (I; R¹= R²= R³= H)]. Fermentation conditions are described for obtaining 5′-hydroxyasperentin (III; R¹= R²= H, R³= OH) from this strain in increased yield. Under these conditions 5′-hydroxyasperentin 8-O-methyl ether (III; R¹= H, R²= Me, R³= OH) is also produced and the known fungal anthraquinone pigments physcion (IV; R¹= Me, R²= H) and questin (IV; R¹= H, R²= Me) are obtained in place of the anthrone derivatives anhydroasperflavin (V) and asperflavin (VI).