An inventory, nutritional analysis and biological evaluation of underutilized indigenous vegetables used to manage non-communicable diseases in Thulamela local municipality, Vhembe District Municipality, South Africa

Abstract

Non-communicable diseases have emerged as a serious public health concern around the world, with a high death rate. The study aim was to document and evaluate the biological activities of underutilized indigenous vegetables used by local people in Thulamela Local Municipality to manage non-communicable diseases. An open structured interview was used to conduct an ethnobotanical survey, and 25 underutilized indigenous vegetables belonging to 13 families were documented. Cucurbitaceae was the dominant family, constituting 21% of the documented species, followed by Urticaceae with 13% of the species. Six of the documented species, which are Citrullus colocynthis, Cleome gynandra, Cucumis africanus, Oxygonum dregeanum, Pouzolzia mixta, and Sonchus oleraceus, were selected and evaluated using standard laboratory procedures for quantifying nutritional, phytochemical constituents, antioxidant, and anti-diabetic activities. The above-mentioned six vegetables contained a considerable amount of important nutrients. Cucumis africanus has the highest levels of ascorbic acid, Ca, Fe, and Mg. In comparison to other vegetables studied, Citrullus colocynthis had the highest levels of total phenolics, total flavonoids, and condensed tannins. The free radical-scavenging activity of all the plant extracts was moderate compared to the positive control (ascorbic acid). On the other hand, dichloromethane and acetone extracts exhibited high antioxidant activity in the beta-carotene-linoleic acid antioxidant system. Most dichloromethane, acetone and distilled water extracts showed low alpha-glucosidase inhibition compared to the positive control (acarbose). However, the dichloromethane extract of Citrullus colocynthis and acetone extract of Cucumis africanus exhibited significantly high alpha-glucosidase inhibitory activity than acarbose. According to the information gathered, people in Thulamela Local Municipality rely on indigenous vegetables for medicine to treat non-communicable diseases. The quantified nutritional and phytochemical contents and the antioxidant and alpha-glucosidase inhibitory activities exhibited by the selected underutilized indigenous vegetables confirm their traditional uses as food and medicine to manage diabetes and other non-communicable diseases. To obtain precise data that can be used to verify these findings, in vivo methods should be used.