Antioxidant, total phenols and proximate constituents of four tropical leafy vegetables

Abstract

Vegetables are the cheapest and readily available sources of vitamins and mineral for most tropical African diets. The aim of this study was to determine the bioactive and proximate characteristics of four (4) indigenous Ghanaian leafy vegetables namely Solanum macrocarpon (Gboma), Talinum fruticosum (Ademe), Corchorus olitorius (Yevogboma) and Amaranthus spp. (Atormaa). Proximate analysis was done according to methods described by AOAC. Total phenolic content (TPC) was determined by the Folin–Ciocalteu method whereas total flavonoid content was determined by aluminum chloride technique. The antioxidant activities of the vegetables were determined by 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay, 2,2-azinobis,3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assay and the Ferric reducing ability of plasma (FRAP) assay. The carbohydrate content of the vegetables studied was the major (59.22%–73.56%) constituent and the least was fat (0.08%–2.65%). The total phenolic and flavonoids content ranged from 0.10 µg GA/g to 9.81 µg GA/g and 363.5 mg QE/g to 1296 mg QE/g respectively. Antioxidant activities of the different vegetables ranged from 1.4% to 70.3% for DPPH activity, ABTS (83%–93%) and FRAP (0.356–0.242). The studied leafy vegetables are good sources of proteins, carbohydrates, fibers and had appreciable ash content and antioxidant activities. Consumption of these leafy vegetables, would help fight degenerative diseases and also improve food and nutrition security. Keywords: Bioactive compounds, Tropical vegetables, Antioxidant activity, Nutritional properties