Nutrient Composition, Phytochemical Content and Anti-Microbial Activity of African Nightshade (Solanum nigrum complex) Edible Berries

Abstract

Although the rights based approach to food has been internationally recognized and incorporated into national policies as a way of curbing food and nutrition insecurity, governments have fallen short of meeting their obligations, making it a global challenge. Hidden hunger is one of the glaring challenges especially in developing countries. Dietary provision with an emphasis on utilization of highly nutritious but neglected and orphaned crops is one alternative of addressing this challenge. African nightshade (Solanum nigrum complex) is one of such plants and its utilization can help in alleviating the burden of hidden hunger. Only the leafy part is utilized even though the plant has edible berries. This study sought to address the underutilization of Solanum nigrum complex by studying the benefits that can be derived from the berries. Berries from four varieties of the plant were harvested at four stages; green, colour break, ripe and at senescence. Chemical analyses of the berries were done to determine the content and changes in macro- and micro-nutrients and the phytochemical content of the berries as they ripened. Antimicrobial activity of the berry extracts was studied and berry-flavoured yoghurt developed and its acceptability amongst consumers tested. Chemical composition of the berries was comparable to other berries with high levels of minerals, vitamin C and carotenoids. As berries ripened, oxalates, total phenols, flavonoids and phytates decreased while Vitamin C, tannins and total carotenoids increased. The berries accumulated glucose and fructose as they ripened with glucose being the most abundant sugar while sucrose recorded a sharp increase at the ripe stage. Size remained relatively constant within each variety while firmness decreased progressively after colour break. Ethanolic berry extracts exhibited antimicrobial potential against fungal and bacterial assays even though the former were more resistant. Gram positive species were the most susceptible. Minimum inhibitory concentration (MIC) of berry extracts ranged from 6.25 µg/ml to 12.5 µg/ml in bacterial assays and 100.00 µg/ml for fungal species. On a 9-point hedonic scale, berry and berry flavoured yoghurts were highly accepted by the consumers, recording acceptability scores of 7.0 and 8.3, respectively. Conclusively, the results of this study confirm that African nightshade berries are of high nutritional potential and can be included in the diet to curb hidden hunger. They can also be applied in the food processing industry as natural preservatives and as valuable ingredients in development of novel functional products with nutraceutical quality.