Microbiological transformation of chromone, chromanone, and ring a hydroxyflavones

Microbial transformation of chromone, chromanone, and 3 ring A hydroxyflavones (5-hydroxy-, 6-hydroxy-, and 7-hydroxyflavones) was attempted using thirty-two microorganisms. While chromone was not biotransformed, chromanone was transformed to chromone and chromanol by Aspergillus niger in 2% yield. Ring A hydroxylated flavones were transformed to the corresponding C-4ʹ hydroxylated metabolites, and the yields and rate of product formation were found to correlate with the distance between the C-4 carbonyl group and the hydroxyl group in ring A.