New scheme of the biosynthesis of formononetin involving 2,7,4 '-trihydroxyisofiavanone but not daidzein as the methyl acceptor

Glycyrrhiza echinata cell-free extract produced isoformononetin by the 7-O- transmethylation of daidzein from S-adenosyl-L-methionine (SAM), When the y east microsome expressing 2-hydroxyisoflavanone synthase was mixed with the cell-free extract and incubated with liquiritigenin and SAM, formononetin emerged, Furthermore, the cell-free extract yielded formononetin on incubat ion with 2,7,4'-trihydroxyisoflavanone and SAM. We propose a novel pathway of formononetin biosynthesis involving 2,7,4'-trihydroxyisoflavanone as the methyl acceptor.