Antioxidant activity of selected Nigerian green leafy vegetables

Green leafy vegetables (GLV) offer a cheap but rich source of micronutrients and other phytochemicals having antioxidant properties and essential for good health. The potential of 21 GLV in the cooked form as natural antioxidant supplements diets was assessed.

The antioxidant activity of hot water extracts of the GLV of Amaranthus hybridus Linn. (Amaranthaceae), Amaranthus caudatus (Amaranthaceae), Beilschmedia manni (Meisn.) Benth. Et Hook.f. (Lauraceae), Celosia argentea var argentea (L.)O.Kuntze (Amarantheceae) Celosia argentea var cristata Linn. (Amarantheceae), Corchorus olitorius L. (Tiliaceae), Crassocephalum crepidioides (Benth). S.Moore (Asteraceae), Gnetum bucholzianum Welw. (Gnetaceae), Gongronema latifolium Benth. (Asclepiadaceae), Heinsia crinita (Afz.) G. Taylor (Rubiaceae), Hibiscus callyphyllus Cav. (Malvaceae), Lasianthera africana P. Beauv (Icacinaceae), Myrianthus arboreus P. Beauv. (Urticaceae), Pterocarpus mildbraedii Harms (Papilionaceae), Pterocarpus santalinoides DC. (Papilionaceae), Solanum macrocarpon L. (Solanaceae), Solanum melongena Linn. (Solanaceae), Struchium sparganophora (Linn.) O. Ktze (Asteraceae), Talinum triangulare (Jacq.) Wild. Portulacaceae, Telferia occidetalis Hook (Curcurbitaceae), Vernonia amygdalina Del. (Asteraceae) were investigated.Potential free radical scanvenging activity of these vegetables was confirmed by spraying spots of the extracts with DPPH(yellow color on purple background). Antioxidant activity was assayed in linoleic acid model system. Total polyphenols as Tannic Acid Equivalent (TAE) and ascorbic acid were evaluated spectrophotometrically.The activity of each extract was calculated as %inhibition of lipid peroxidation. The extracts showed marked antioxidant activity in linoleic acid model systems. Antioxidant values ranged from as low as 3.67% in A. hybridus to as high as 68.41% in C. argentea var cristata. Phenol content varied from 21.83mg/100g dry weight in T. triangulare to 546.97mg/100g dry weight in G. bucholzianum. Ascorbic acid content was from 13.41mg/100g dry weight in V. amygdalina to 187.11mg/100g dry weight in G. latifolium. There was no correlation (R²=–0.432) between antioxidant activity, total phenols and ascorbic acid content.