Biotransformation of sesaminol triglucoside to mammalian lignans by intestinal microbiota

Plant lignans occur widely in foods, with flaxseed recognized as their richest source. Some plant lignans can be converted by intestinal microbiota to the mammalian lignans, enterodiol and enterolactone, which may have protective effects against hormone-related diseases such as breast cancer. This study determined whether plant lignans in sesame seed, particularly sesaminol triglucoside (STG), could be metabolized to mammalian lignans. STG is a furofuran lignan with methylenedioxyphenyls. The transformation of furofuran lignans to mammalian lignans by intestinal microbiota involves the hydrolysis of glucoside, demethylenation of a methylene group, oxidation of dibenzylbutanediol to dibenzylbutyrolactone, and reductive cleavage of furofuran rings. STG has methylenedioxyphenyl moieties in their structures that may require additional oxidative demethylenation of the methylenedioxyphenyl ring for conversion to mammalian lignans. However, STG is metabolized, via intestinal microbiota, to a catechol moiety. The major STG metabolite was characterized as 4-[((3R,4R)-5-(6-hydroxybenzo[d][1,3]dioxol-5-yl)-4-(hydroxymethyl)tetrahydrofuran-3-yl)methyl]benzene-1,2-diol using NMR and mass spectrometry, and STG could be converted to enterolactone and enterodiol by rat intestinal microflora.