Nutraceutical properties of wild fruit plants in Mpumalanga.

Abstract

Nutraceuticals have emerged as reliable substances for managing health conditions by providing both nutrition and phytotherapy. Wild fruit plants, with a long history of use by local communities for nutritional and medicinal purposes, represent promising candidates for nutraceutical development. This study aimed to explore the nutraceutical properties of wild fruit plants harvested from Bushbuckridge local municipality, Mpumalanga Province, South Africa. A comprehensive literature survey on wild fruit plants in Mpumalanga Province identified five key studies documenting a total of 83 wild fruit plant species from 61 genera and 31 families. The review highlighted research gaps, including the need to explore under-documented regions and variations in the cultural use of these plants across different ethnic groups. Based on their medicinal and nutritional uses, frequency of citation, and research gaps, six wild fruit plants were selected for further investigation: Carissa spinarum L., Diospyros mespiliformis Hochst. ex A.DC., Euclea crispa (Thunb.) Gürke, Ficus thonningii Blume, Strychnos spinosa Lam., and Strychnos madagascariensis Poir. The antimicrobial activity of the leaves of these plant species were tested against the bacterial skin pathogens Klebsiella pneumoniae and Pseudomonas aeruginosa. Using disc diffusion, the hexane extracts of D. mespiliformis and E. crispa had an inhibition zone of 28 mm against P. aeruginosa. The microdilution assay also revealed that the methanol extract of D. mespiliformis exhibited the strongest activity against both pathogens, with a minimum inhibitory concentration (MIC) ranging from 0.781 to 1.563 mg/mL. The antioxidant potential of the plant leaves was determined using 2,2-diphenyl-1-picryhydrazyl (DPPH) and Ferric Reducing Antioxidant Power (FRAP) assays. The methanol extract of E. crispa demonstrated potent antioxidant activity, with a half-maximal inhibitory concentration (IC50) of 1.42 μg/mL, comparable to standard ascorbic acid. Other species, including C. spinarum and S. spinosa, also showed promising antioxidant activity, highlighting their potential to mitigate oxidative stress-related conditions. The nutritional and mineral compositions of F. thonningii fruits and the pulp, peel, and seeds of D. mespiliformis and S. spinosa were analysed. The proximate analysis of the fruits revealed significant protein and fibre content. The elemental analysis of the leaves and fruit showed a wide range of minerals present in the leaves and fruit. Notably, S. spinosa peels contained 44.21% fibre, while its leaves were rich in manganese (1,728 mg/kg). Elemental analysis identified essential minerals like calcium, iron, and magnesium, but also detected heavy metals, such as arsenic, cadmium, and chromium, in the fruits, posing potential toxicity risks. The study demonstrates that wild fruit plants possess significant nutraceutical potential due to their antimicrobial, antioxidant, and nutritional properties. These findings validate their traditional uses and underscore their potential role in addressing food insecurity, managing health disorders, and developing nutraceutical products.