Sesame Seed Lignans Diversity, Human Metabolism and Bioactivities

Moazzami, A.A. 2006. Sesame Seed Lignans Diversity, Human Metabolism and Bioactivity. Doctor’s dissertation. ISSN 1652-6880, ISBN 91-576-7147-8 Sesame seed has been an important oilseed since ancient times. It contains 25% protein and 50% oil. Sesame seed possesses many health promoting effects, some of which have been attributed to a group of compounds called lignans (sesamin, sesamolin, sesaminol and sesamolinol). Sesame seed contains lignan aglycones in oil and lignan glucosides. Sesamin, the major sesame oil lignan, is known to reduce plasma cholesterol and to increase plasma γ-tocopherol in humans. This thesis aimed at investigating the content of lignan and lignan glucosides in sesame seeds, human metabolism of sesamin and the effect of possible interaction between sesamin and phytosterols on the bioactivity of sesamin. To these purposes, two new lignan glucosides, sesaminol diglucoside and sesamolinol diglucoside, were isolated from sesame seeds and characterized by LC-MS and NMR. A method for the analysis of sesame lignan glucosides was developed based on extraction of defatted sesame flour with 85% and 70% ethanol and using naringenin as internal standard and a reversed phase HPLC-DAD. A quantitative NMR technique was also developed to analyze the urinary metabolite of sesamin in humans based on using methylenedioxyphenyl signal (δ 5.91) in H-NMR spectra of deconjugated urine extracts to measure the metabolite(s) content. A diversity of sesame seed oil and products were analyzed for their content of lignans and lignan glucosides. It was shown that sesame seeds contain almost 0.6% of lignans and 32% of lignans are in glucosylated form of sesaminol and sesamolinol. In a human study, volunteers (n=6) consumed a single dose of muffins backed with sesame oil containing sesamin and sesamolin. It was shown that almost 30% of sesamin ingested is excreted in urine in the form of a major catechol metabolite. In an animal experiment, rats were fed diet containing two concentrations of sesamin and phytosterols. It was shown that phytosterols reduce the lipid modulating effects of sesamin on γ-tocopherol and dihomo-γ-linolenic acid. Overall, the findings from this thesis show that sesame seed is a rich source of lignans and that at least 30% of sesamin is absorbed in human, however the form of absorption is to be elucidated. Moreover, the biopotency of sesamin was reduced when the concentration of phytosterols was increased in the diet possibility because of reduction in the bioavailability of sesamin.