Gut microbial O-dealkylation of isoflavone derivatives by Blautia sp. MRG-PMF1

The anaerobic bacterium Blautia sp. MRG-PMF1 is known for its ability to biotransform aryl methyl ether and allyl aryl ether substrates via a cobalamin-dependent O -demethylase system. To investigate the substrate promiscuity of this corrinoid-dependent O -demethylase, we examined its activity toward isoflavone derivatives bearing alkoxy substituents other than methoxy groups. Remarkably, Blautia sp. MRG-PMF1 efficiently converted a range of 7-alkoxyisoflavones into 7-hydroxyisoflavone. To elucidate the reaction mechanism of this newly identified cobalamin-dependent O -dealkylase, O -dealkylation activity was assessed using cell-free extracts. The observed reactivity followed the order of O -ethyl > O -methyl > O -propyl > O -isopropyl, suggesting that cleavage of the alkyl ether group proceeded through an S N 2-type mechanism rather than a radical pathway. This study demonstrated for the first time that the cobalamin-dependent O -demethylase system could extend its activity to O -dealkylation, highlighting the broader metabolic capacity of the human gut microbiota to process diverse dietary natural products.