Abstract
BACKGROUND: Oils from various sources are vital nutritional components with a variety of roles in our body. Niger seed (Guzoita abyssinica) is endemic to Ethiopia and is among the major oil seed crops grown in the country. The fatty acid composition and the concentration of other bioactive phytochemicals in it vary with species type, geographical origin, cultivation season, and varietal types. The present work investigated the fatty acid profile and the total phenolic (TPC), total flavonoid content (TFC) and antioxidant activity (AA) of Niger seed samples obtained from five different zones in the Amhara and Oromia regions of Ethiopia. using internationally accepted standard methods. RESULTS: In all the samples, its main unsaturated acids were linoleic acid, ranging between 67.30 and 74.67% with respect to the relative percentage comprising 179 to 234 mg/g in terms of concentration; oleic acid constitutes between 5.43 and 11.02% of the total fatty acid or 1.03 and 1.60 mg/g of dry matter. Among saturated acids, it was the most abundant palmitic acid, ranging between 10.32 and 10.66% of the entire fatty acids comprising 24.80 to 37.10 mg/g. Amongst the zones, the seed from Amhara region, specifically from North Gondar has been the richest regarding a total of 347.74 mg/g. In addition, the total phenolic content ranged between 10.89 and 11.78 mg GAE/g, whereas the content of total flavonoids ranged from 5.42 to 6.67 mg CE/g. Aqueous methanol (80%) extracted more phenolic content than absolute methanol. On a regional basis, the Amhara region, represented by the North Gondar and East Gojjam zones of the study area, had relatively higher TPC and TFC than other regions. The DPPH scavenging assay IC50 value (μg/mL) ranged between 133-188 μg/mL and poorly correlated with TPC. CONCLUSION: Among the different fatty acids obtained, four of them, linoleic, oleic, palmitic, and stearic acids, are the major ones, followed by a significant amount of phenolic compounds irrespective of the variety of the studied samples and sampling of locations. The study also confirmed that TPC and TFC are not the only phytochemicals responsible for the antioxidant activity of the niger sees, as was reflected by the poor correlation between TPC and AA activity. Hence these findings indicate that the seeds of Niger could be an important source of essential fatty acids and medicinally important phytochemicals important for nutritional health improvement and agricultural development in Ethiopia.