Demethylation of Polymethoxyflavones by Human Gut Bacterium, <i>Blautia</i> sp. MRG-PMF1

Polymethoxyflavones (PMFs) were biotransformed to various demethylated metabolites in the human intestine by the PMF-metabolizing bacterium, <i>Blautia</i> sp. MRG-PMF1. Because the newly formed metabolites can have different biological activities, the pathways and regioselectivity of PMF bioconversion were investigated. Using an anaerobic in vitro study, 12 PMFs, 5,7-dimethoxyflavone (5,7-DMF), 5-hydroxy-7-methoxyflavone (5-OH-7-MF), 3,5,7-trimethoxyflavone (3,5,7-TMF), 5-hydroxy-3,7-dimethoxyflavone (5-OH-3,7-DMF), 5,7,4′-trimethoxyflavone (5,7,4′-TMF), 5-hydroxy-7,4′-dimethoxyflavone (5-OH-7,4′-DMF), 3,5,7,4′-tetramethoxyflavone (3,5,7,4′-TMF), 5-hydroxy-3,7,4′-trimethoxyflavone (5-OH-3,7,4′-TMF), 5,7,3′,4′-tetramethoxyflavone (5,7,3′,4′-TMF), 3,5,7,3′,4′-pentamethoxyflavone (3,5,7,3′,4′-PMF), 5-hydroxy-3,7,3′,4′-tetramethoxyflavone (5-OH-3,7,3′,4′-TMF), and 5,3′-dihydroxy-3,7,4′-trimethoxyflavone (5,3′-diOH-3,7,4′-TMF), were converted to chrysin, apigenin, galangin, kaempferol, luteolin, and quercetin after complete demethylation. The time-course monitoring of PMF biotransformations elucidated bioconversion pathways, including the identification of metabolic intermediates. As a robust flavonoid demethylase, regioselectivity of PMF demethylation generally followed the order C-7 > C-4′ ≈ C-3′ > C-5 > C-3. PMF demethylase in the MRG-PMF1 strain was suggested as a Co-corrinoid methyltransferase system, and this was supported by the experiments utilizing other methyl aryl ether substrates and inhibitors

Curcuminoid Demethylation as an Alternative Metabolism by Human Intestinal Microbiota

Curcumin and other curcuminoids from Curcuma longa are important bioactive compounds exhibiting various pharmacological activities. In addition to the known reductive metabolism of curcuminoids, an alternative biotransformation of curcuminoids by human gut microbiota is reported herein. A curcuminoid mixture, composed of curcumin (<b>1</b>), demethoxycurcumin (<b>2</b>), and bisdemethoxycurcumin (<b>3</b>), was metabolized by the human intestinal bacterium Blautia sp. MRG-PMF1. <b>1</b> and <b>2</b> were converted to new metabolites by the methyl aryl ether cleavage reaction. Two metabolites, demethylcurcumin (<b>4</b>) and bisdemethylcurcumin (<b>5</b>), were sequentially produced from <b>1</b>, and demethyldemethoxycurcumin (<b>6</b>) was produced from <b>2</b>. Until now, sequential reduction of the heptadienone backbone of curcuminoids was the only known metabolism to occur in the human intestine. In this study, a new intestinal metabolism of curcuminoids was discovered. Demethylation of curcuminoids produced three new colonic metabolites that were already known as promising synthetic curcumin analogues. The results could explain the observed beneficial effects of turmeric