Quantitative NMR analysis of a sesamin catechol metabolite in human urine

Sesamin, the major sesame oil lignan, is recognized for its health-promoting effects, including the lowering of cholesterol and elevation of γ-tocopherol in rats and humans. However, little is known about the absorption and metabolism of sesamin in humans. In this study, 6 healthy volunteers took a single dose of sesame oil (508 μmol sesamin) and their urine was collected for four 12-h periods. The urine samples were treated with β-glucuronidase/sulphatase and extracted with chloroform. The major urinary sesamin metabolite in the chloroform extract was collected using HPLC diode array detector and characterized as (1R,2S,5R,6S)-6-(3,4-dihydroxyphenyl)-2-(3, 4-methylenedioxyphenyl)-3,7-dioxabicyclo-[3,3,0]octane using NMR and mass spectroscopy. A quantitative ¹H-NMR technique, based on the methylenedioxyphenyl protons signal (δ 5.91), was used for the quantification of the metabolite in the chloroform extracts of urine. The excretion of the sesamin catechol metabolite ranged from 22.2 to 38.6% (mean ± SD, 29.3 ± 5.6) of the ingested dose and happened mainly in the 1st 12 h after ingestion.