Biotransformation of isoflavones by Aspergillus niger, as biocatalyst

Biotransformation of the isoflavones, daidzein (1), 7,4′-dimethoxyisoflavone (2) and 7,4′-3 diacetoxyisoflavone (3), by Aspergillus niger was investigated. Compound 1 was hardly four metabolized by A. niger, while compound 2 was transformed to 6-hydroxy-7,4′-5 dimethoxyisoflavone (4) and daidzein (1) and compound 3 was transformed to daidzein (1). This suggested that 2 was converted to 4 by oxidation at the C-6 position and to 1 by demethylation of methoxy groups at the C-7 and C-4′ positions. Compound 3 was converted to 1 by hydrolysis at the C-7 and C-4′ positions.