VARIATIONS IN THE COMPOSITION OF STEROLS, TOCOPHEROLS AND LIGNANS IN SEED OILS FROM 4 SESAMUM SPECIES

Seeds from different collections of cultivated Sesamum indicum Linn an d three related wild species [specifically, S. alatum Thonn., S. radia tum Schum and 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. indic um (1.4-1.8%), mainly due to their high contents of lignans. Total ste rols accounted for ca 40, 22, 20 and 16% of the unsaponifiables of the four species, respectively. The four species were different in the re lative percentages of the three sterol fractions (the desmethyl, monom ethyl and dimethyl sterols) and in the percentage composition of each fraction. Campesterol, stigmasterol, sitosterol and Delta(5)-avenaster ol were the major desmethyl sterols, whereas obtusifoliol, gramisterol , cycloeucalenol and citrostandienol were the major monomethyl sterols , and alpha-amyrin, beta-amyrin, cycloartenol and 24 methylene cycloar tanol were the main dimethyl sterols in all species. Differences were also observed among the four species in sterol patterns of the free st erols compared to the sterol esters. Sesamum alatum contained less toc opherols (210-320 mg/kg oil), and S. radiatum and S. angustifolium con tained more tocopherols (ca 750 and 800 mg/kg oil, respectively) than did S. indicum (490-680 mg/kg oil). The four species were comparable i n tocopherol composition, with gamma-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 se samin and sesamolin (0.01% each). Sesamum radiatum was rich in sesamin (2.40%) and contained minor amounts of sesamolin (0.02%), where S. an gustifolium was rich in sesangolin (3.15%) and also contained consider able amounts of sesamin (0.32%) and sesamolin (0.16%).