Variations in the composition of sterols, tocopherols and lignans in seed oils from four Sesamum species

Seeds from different collections of cultivated Sesamum indicum Linn and three related wild species [specifically, S. alatum Thonn., S. radiatum Schum & Thonn. and S. angustifolium (Oliv.) Engl.] were studied for their oil contents and fatty acid composition of the total lipids. The oils from wild seeds were characterized by higher percentages of unsaponifiables (4.9, 2.6 and 3.7%, respectively) compared to S. indicum (1.4-1.8%), mainly due to their high contents of lignans. Total sterols accounted for ca. 40, 22, 20 and 16% of the unsaponifiables of the four species, respectively. The four species were different in the relative percentages of the three sterol fractions (the desmethyl, monomethyl and dimethyl sterols) and in the percentage composition of each fraction. Campesterol, stigmasterol, sitosterol and Δ⁵-avenasterol were the major desmethyl sterols, whereas obtusifoliol, gramisterol, cycloeucalenol and citrostandienol were the major monomethyl sterols, and α-amyrin, β-amyrin, cycloartenol and 24-methylene cycloartanol were the main dimethyl sterols in all species. Differences were also observed among the four species in sterol patterns of the free sterols compared to the sterol esters. Sesamum alatum contained less tocopherols (210-320 mg/kg oil), and S. radiatum and S. angustifolium contained more tocopherols (ca. 750 and 800 mg/kg oil, respectively) than did S. indicum (490-680 mg/kg oil). The four species were comparable in tocopherol composition, with γ-tocopherol representing 96-99% of the total tocopherols. The four species varied widely in the identity and levels of the different lignans. The percentages of these lignans in the oils of S. indicum were sesamin (0.55%) and sesamolin (0.50%). Sesamum alatum showed 1.37% of 2-episesalatin and minor amounts of sesamin and sesamolin (0.01% each). Sesamum radiatum was rich in sesamin (2.40%) and contained minor amounts of sesamolin (0.02%), where S. angustifolium was rich in sesangolin (3.15%) and also contained considerable amounts of sesamin (0.32%) and sesamolin (0.16%).