A detailed study of the biotransformation of 6- and 7-methoxyflavones by four fungal strains (Aspergillus niger strains MB, KB, and SBP; Penicillium chermesinum 113) was carried out. Products of demethylation and also demethylation combined with hydroxylation at C-4' were identified. The biotransformation products were stronger antioxidants than the substrates.