A Comparative Study on Antioxidant Potential of Selected African and Exotic Leafy Vegetables

Abstract

African leafy vegetables (ALVs) are thought to contain an immense variety of antioxidants, which may provide nutritional and health benefits. However, there is limited, robust, and comparable information describing their nutritional composition. The aim of this study is to determine the antioxidant potential of selected ALVs [black jack (Bidens pilosa L.) and amaranth (Amaranthus hybridus L.)] in comparison with exotic leafy vegetables (ELVs) [lettuce (Lactuca sativa L.), green cabbage (Brassica oleracea), red cabbage (B. oleracea var. capitata)]. Different nonenzymatic and enzymatic antioxidant assays were used to determine plant carbohydrates (CHOs) using high-performance liquid chromatography (HPLC), phenols (Folin–Ciocalteu), ascorbic acid, carotenoids, total antioxidant capacity (TAOC) using reducing ferric ion antioxidant potential (FRAP) and 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH) assays, super oxide dismutase (SOD), catalase (CAT), and peroxidase (POD). Both amaranth and black jack produced high levels of CHOs, carotenoids, ascorbic acid, and phenols during early vegetative growth [4 weeks after transplanting (WAT)]. Similarly, SOD, CAT, and POD activity for amaranth and black jack also increased during early vegetative development. Conversely, exotic vegetables (lettuce and cabbages) only increased these antioxidants toward maturity. Overall, ALVs have produced higher concentrations of antioxidants specifically during early vegetative growth stage than the exotic vegetables. The promotion of ALVs could promote a healthy alternative especially in poor rural households.