Antioxidant Potentialities of Black Nightshade and Sweet Potatoes Leaves Consumed in Côte d’Ivoire

Leafy vegetables contain nutrients and have also antioxidant potentialities. Two of them, black nightshade and sweet potatoes leaves, were analyzed for their antioxidant capacities. Total phenolic and flavonoids were determined. The antioxidant activities determinations were on radical scavenging activities, lipid peroxidation inhibition and reducing power. The results showed that total phenolic and flavonoids content were higher in sweet potatoes leaves than in black nightshade. Indeed, sweet potatoes total phenolic and flavonoids content were respectively 933.30 ± 15.30 mg Gallic Acid Equivalent (GAE)/g of dry matter (DM) and 149.00 ± 4.00 mg Quercetin Equivalent (QE)/g DM, while that of black nightshade were 300.00 ± 5.7 mg GAE/g DM and 54.60 ± 8.30 mg QE/g DM. Consequently, sweet potatoes leaves had best antiradical activities which were characterised by their IC50 value (3.12 ± 1.42µg/ml). That of black nightshade was 163.00 ± 0.82 µg/ml. The two leafy vegetables had a lipid peroxidation inhibitory capacities upper than that of gallic acid and these inhibitory capacities were more important in sweet potatoes leaves than in black nightshade leaves. Sweet potatoes leaves IC50 was about 206.33 ± 14.05 µg/ml and that of black nightshade was 272.33 ± 21.39 µg/ml. However, reducing power in leaves was lower than that of vitamin C (the molecular reference). Antioxidant activities were high in sweet potatoes leaves. But, it could decrease after cooking process as nutrients losses are occurred during cooking.