Heavy Metal, Proximate and Antioxidant Composition of Five Cultivars of Cowpea (Vigna unguiculata) in Ibadan, Oyo State Nigeria

Five commonly consumed cultivars of cowpea (local names: Olo, Drum, Oloyin, Oloyin milk and Sokoto) were obtained from major market (bodija) Ibadan and were evaluated for heavy metals (Cd, Cr, Ni, Hg, Pb and Ar), proximate (crude protein, fat, crude fibre, moisture and Ash contents) and Phytochemicals (Flavonoid and Phenolic contents). The result shows that, Ar and Ni contents are significantly high amongst the heavy metals for the cultivars examined which is within value range of 0.02-0.13 mg/g d.w. and 0.0017-0.036 mg/g respectively. Oloyin cultivar has the highest Ar contents above tolerance limit above of 0.10 mg/g d.w. The value range of crude protein, fat, crude carbohydrate, crude fibre, moisture and ash contents of the cultivars examined are 26.00-33.00 mg/g d.w., 1.60-2.30 mg/g d.w., 59.0-63.00 mg/g d.w., 2.30-3.20 mg/g d.w., 1.20-4.40 mg/g d.w., 0.80-3.70 mg/g d.w. respectively. The total heavy metal compositions among the cultivars follow this order; Oloyin > Oloyin milk > Sokoto > Drum > Olo. The order for proximate composition is Oloyin milk > Oloyin > Olo > Drum > Sokoto. For flavonoid content, the order is Olo > Oloyin > Sokoto > Drum > Oloyin milk, for phenolics content, the order is Olo > Drum > Oloyin milk > Sokoto > Oloyin.