Effect of Extraction Solvent on Oil and Bioactives Composition of Commercial Indian Niger (Guizotia abyssinica (L.f.) Cass.) Seed

Commercially available niger (Guizotia abyssinica (L.f.) Cass.) seed was investigated to evaluate the effect of extraction solvent on oil and bioactives composition. For this purpose, niger seeds were subjected to solvent extraction using solvents of different polarity, viz., hexane, petroleum ether, chloroform, acetone, methanol and ethanol. The oil content of niger seeds obtained after extraction with solvents of different polarities was in the range of 31.8-41.3 g/100 g. The extracted oil was characterized by the following parameters: color (40.0-95.0 Lovibond units), free fatty acids (3.6-12.3 g/100 g), peroxide value (3.2-7.8 mequiv O-2/kg), iodine value (137.6-140.3 cg I-2/g), saponification value (177.3-185.9 mg KOH/g) and unsaponifiable matter (1.3-4.3 g/100 g). Among fatty acids, linoleic acid (69.4-73.2 %) was the major fatty acid and trilinolein (31.2-33.4 %) was the major triacylglycerol. The composition of bioactive molecules was 171.9-345.8 ppm of total tocopherols; 247.1-2,647.7 ppm of total phenolics; 1,249.6-6,309.3 ppm of total sterols and 18.9-181.0 ppm of total carotenoids. Among the tocopherols, alpha-tocopherol was the major component with 154-276 ppm. Of the total phenolics, vanillic acid with 176-1,709 ppm was the major phenolic compound in the oil extracted using different solvents. Ethanol-extracted oil showed a 13.9-fold better oxidative stability and a higher radical scavenging activity (IC50 value of 9.2 mg/mL) compared to hexane-extracted oil (IC50 value of 40.3 mg/mL). This is probably the first report of its kind on solvent extractability of bioactives of niger seed.