Antioxidant Activity by DPPH Assay of Crude Methanolic Extracts from Selected Indigenous Vegetables in Kenya

Abstract

Antioxidants are natural or synthetic biological molecules that prevent cell damage by averting free radical formation, scavenging, or promoting their decomposition. When the body’s ability to counteract free radicals is overburdened, oxidative stress develops, triggering several diseases. Indigenous vegetables are beneficial sources of nutrition that can supply the recommended daily allowance of nutrients with antioxidants. In this study, five indigenous vegetables (Cleome gynandra, Solanum nigrum, Basella Alba, Cucurbita argyrosperma, and Amaranthus blitum) collected from local markets in Kenya were investigated for the presence of antioxidants using the two assays: 2, 2-Diphenyl-1-picrylhydrazyl (DPPH) and Thin Layer Chromatography (TLC). 100 µg/ml of the crude extract was spotted on the Alugram Xtra GUV254 TLC plate. The chromatogram was developed using methanol (95% volume): ethylacetate (5% volume). The dried chromatogram was sprayed with DPPH (0.15 % w/v) solution and examined after 30 minutes. The positive control of this assay was vitamin C. Total flavonoid and phenol contents were used to validate the antioxidants present. A stable DPPH radical is purple in color, on reduction it changed to yellow diphenyl picryl hydrazine compound, indicating active free-radical scavenging compounds present in the crude extracts. The intensity of the yellow color denoted their high scavenging ability. The antioxidants, phenolic and flavonoid contents had a good correlation in a dose-dependent manner. These results indicated indigenous vegetables contain antioxidant compounds. This study recommends investigation using In-vitro antioxidant assays on each of the crude extracts to determine their scavenging capacities and spectroscopy to determine the structure of the active antioxidant compounds. The study equally recommends a comparative study on indigenous vegetables from different ecological zones to determine the geographical influence of the availability of antioxidants. Promoting the use of indigenous vegetables and maximizing their potential for food can help accomplish some objectives of Vision 2030 and the Sustainable Development Goals.