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

Abstract

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.

Natural polyphenol disposition via coupled metabolic pathways

“…For example, CYP catalyzed the formation of genistein from biochanin A [85,86]. In animals and humans, this demethylation reaction has been detected following red clover and kaempferol administrations [87][88][89]. However, CYP catalyzed metabolism of polyphenols represents a minor metabolic pathway when comparing to phase II metabolism.…”

Synthesis, Characterization, and Antioxidant Activities of Genistein, Biochanin A, and Their Analogues

“…Genistein can bind to both the Estrogen Receptor alpha (ER ) and the Estrogen Receptor beta (ER ), although it has a higher affinity for the ER [19], and genistein is thought to exert its estrogenic effects through mechanisms similar to those of estradiol [20]. Biochanin A ( ) is the 4 -O-methyl derivative of genistein and biochanin A is the predominant isoflavone found in alfalfa, Trifolium pratense, and Cicer arietinum [21] which has an inhibitory and apoptogenic effect on certain cancer cells such as pancreatic cancer and prostate cancer [22,23].…”

Phytochemical profiling of underexploited Fabaceae species: Insights on the ontogenic and phylogenetic effects over isoflavone levels

“…In fact, the high contents of biochanin A detected in both Lotus species and B. pelecinus represent a promising result considering that this O-methylated isoflavone is acknowledged for its neuroprotective (Wang et al, 2015), cardioprotective, nephroprotective (Jalaludeen et al, 2015), antitumoral (Piegholdt et al, 2014), antiviral and anti-inflammatory (Sithisarn, Michaelis, Schubert-Zsilavecz, & Cinatl, 2013) activities. Furthermore, biochanin A might suffer demethylation by human hepatic enzymes, yielding genistein, which is also acknowledged for its biological activity (Tolleson, Doerge, Churchwell, Marques, & Roberts, 2002). In Biserrula and Lotus genera, the genistein levels were similar to those reported in widely acknowledged species, e.g., soybean, in which genistein was reported as the major isoflavone (84 to 583 mg/kg dm), depending on the reproductive stages (Kumar, Rani, Dixit, Bhatnagar, & Chauhan, 2009).…”