Metabolism of Biochanin A and Formononetin by Human Liver Microsomes in Vitro

• Published in: Journal of agricultural and food chemistry Vol. 50; no. 17; pp. 4783 - 4790
• Main Authors: Tolleson, William H, Doerge, Daniel R, Churchwell, Mona I, Marques, M. Matilde, Roberts, Dean W
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 14-08-2002
• Subjects: Animals; Biological and medical sciences; Chromatography, High Pressure Liquid; Cytochrome P-450 Enzyme System - metabolism; Food industries; Food toxicology; Fundamental and applied biological sciences. Psychology; General pharmacology; Genistein - metabolism; Humans; Hydroxylation; Isoenzymes - metabolism; Isoflavones - metabolism; Kinetics; Magnetic Resonance Spectroscopy; Mass Spectrometry; Medical sciences; Methylation; Microsomes, Liver - enzymology; NADP - metabolism; Pharmacognosy. Homeopathy. Health food; Pharmacology. Drug treatments; Rats; Human; Cytochrome P450; Liver; Genistein; Identification; Microsome; Metabolism; Isoflavone derivatives; In vitro; Biological activity; Phytoestrogen; Characterization; Demethylation; Isolation; Daidzein; Nuclear magnetic resonance; Mass spectrometry
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf025549r

Biochanin A and formononetin are abundant in legumes. These proestrogenic isoflavones can be converted by 4‘-O-demethylation to the more potent phytoestrogens genistein and daidzein. Incubation of biochanin A or formononetin with human liver microsomes resulted in 4‘-O-demethylation and the production of additional metabolites. Three new hydroxylated formononetin derivatives, 6,7-dihydroxy-4‘-methoxyisoflavone, 7,8-dihydroxy-4‘-methoxyisoflavone, and 7,3‘-dihydroxy-4‘-methoxyisoflavone, were isolated and characterized. We surveyed the O-demethylase competence of cytochrome P450 isoforms found in human liver. Human cytochrome P450 isoforms 1A2, 2E1, 2C9*1, 2C19, and 2D6*1 catalyzed biochanin A consumption and genistein production. Human cytochrome P450 isoforms 1A2, 2C9*1, 2A6, 2D6*1, and 2C19 catalyzed formononetin consumption and daidzein production. These isoforms also generated other hydroxylated metabolites. Although O-demethylation of isoflavones has been attributed to metabolism by gut microflora, our study demonstrates that human hepatic microsomal enzymes can perform the same transformation and may play a key role in the conversion of 4‘-O-methylated isoflavones to more potent phytoestrogens. Keywords: Isoflavone metabolism; cytochrome P450; biochanin A; formononetin