Variation in fatty acid composition of the different acyl lipids 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 and Thonn. and S. angustifolium (Oliv.) Engl.] were studied for their oil content and fatty acid composition of the total lipids. The wild seeds contained less oil (ca. 30%) than the cultivated seeds (ca. 50%). Lipids from all four species were comparable in their total fatty acid composition, with palmitic (8.2-12.7%), stearic (5.6-9.1%), oleic (33.4-46.9%) and linoleic acid (33.2-48.4%) as the major acids. The total lipids from selected samples were fractionated by thin-layer chromatography into five fractions: triacylglycerols (TAG; 80.3-88.9%), diacylglycerols (DAG; 6.5-10.4%), free fatty acids (FFA; 1.2-5.1%), polar lipids (PL; 2.3-3.5%) and steryl esters (SE; 0.3-0.6%). Compared to the TAG, the four other fractions (viz, DAG, FFA, PL and SE) were generally characterized by higher percentages of saturated acids, notably palmitic and stearic acids, and lower percentages of linoleic and oleic acids in all species. Slightly higher percentages of long-chain fatty acids (20:0, 20:1, 22:0 and 24:0) were observed for lipid classes other than TAG in all four species. Based on the fatty acid composition of the total lipids and of the different acyl lipid classes, it seems that S. radiatum and S. angustifolium are more related to each other than they are to the other two species.