VARIATION IN LIPID-COMPOSITION OF NIGER SEED (GUIZOTIA-ABYSSINICA CASS) SAMPLES COLLECTED FROM DIFFERENT REGIONS IN ETHIOPIA

Niger seed samples were collected from different regions in Ethiopia for determination of oil content, and of fatty acid, tocopherol and sterol composition in the seed oil by gas-liquid chromatography and high-performance liquid chromatography methods. There was a large variation in oil content, ranging from 29 to 39%. More than 70% of the fatty acids was linoleic acid (18:2) in all samples analyzed. The other predominant fatty acids were palmitic (16:0), stearic (18:0) and oleic (18:1) at a range of 6 to 11% each. Total polar lipids recovered after preparative thin-layer chromatography comprised a small fraction of the total lipids. They had higher 16:0 and lower 18:2 contents than the triacylglycerols. alpha-Tocopherol was the predominant tocopherol in all samples, 94-96% of the total amounting to 630-800 mu g/g oil. More than 40% of the total sterols was beta-sitosterol, ca. 2000 mu g/g oil. The other major sterols were campesterol and stigmasterol, ranging from 11 to 14%. The Delta 5- and Delta 7-avenasterols were in the range of 4 to 7%. From the samples studied, no conclusion could be drawn regarding the influence of altitude or location on oil content, tocopherol and/or sterol contents. The results of the present study on niger seed oil are discussed in comparison with known data for common oils from Compositae, viz, safflower and sunflower.