Plant
lignans occur in many foods, with flaxseed presently recognized as the 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
sesamin, could be metabolized to the mammalian
lignans. The total plant
lignan concentration in sesame seed (2180 micromol/100 g) was higher than that in flaxseed (820 micromol/100 g). In vitro fermentation with human fecal inoculum showed conversion of
sesamin to the mammalian
lignans, although at a lower rate (1.1%) compared with that of
secoisolariciresinol diglucoside (57.2%). However, when fed to female Sprague-Dawley rats for 10 d,
sesamin (15 mg/kg
body weight) and
a 10% sesame seed diet resulted in greater (P < 0.05) urinary mammalian
lignan excretion (3.2 and 11.2 micromol/d, respectively), than the control (< 0.05 micromol/d). We conclude that sesame seed is a rich source of mammalian
lignan precursors and
sesamin is one of them. From intermediate metabolites of
sesamin identified in rat urine by GC-MS, a tentative metabolic pathway of
sesamin to mammalian
lignans is suggested.