Microbial metabolism. Part 10: Metabolites of 7,8-dimethoxyflavone and 5-methoxyflavone

Microbial transformation of 7,8-dimethoxyflavone (1) by Mucor ramannianus produced five metabolites: 7,8-dimethoxy-4'-hydroxyflavone (2), 3',4'-dihydroxy-7,8-dimethoxyflavone (3), 7,3'-dihydroxy-8-methoxyflavone (4), 7,4'-dihydroxy-8-methoxyflavone (5) and 8-methoxy-7,3',4'-trihydroxyflavone (6). It was, however, completely converted to a single metabolite, 7-hydroxy-8-methoxyflavone (7) by Aspergillus flavus. 5-Methoxyflavone (8), when fermented with Beauveria bassiana, gave a single product, 5-methoxyflavanone (9). Conversion of 8 with Aspergillus alliaceus yielded the metabolite 4'-hydroxy-5-methoxyflavone (10). The structures of the compounds 2-7, 9 and 10 were established by spectroscopic methods.