Screening of selected edible wild fruits from the Tswapong region (Botswana) for their antioxidant and antimicrobial potential

Abstract

In recent years, accumulating studies on traditional edible plants species have shown potential Pharmaceutical and health benefits including antioxidant, anticancer, anti-aging, antiatherosclerosis, antimicrobial and anti-inflammatory activities. There are limited studies on traditional edible plant species of Botswana. In this study, seven edible wild fruits (Vangueria infausta, Ximenia americana, Ximenia caffara, Grewia flava, Gweria cana Grewia bicolor and Mimusops zeyheri) were extracted with ethanol, distilled water and methanol and the pulp extract were investigated for their phytochemical properties, antioxidant and antimicrobial potential. Ximenia spp. showed the presence of phenols, saponins, terpenoids and tannins, while Grewia spp., Mimusops zeyheri and Vangueria infausta showed the presence of phenols, saponins and terpenoids as screening by qualitative method. Methanolic extract of Ximenia. Caffra showed significantly higher total flavanoid content (TFC) and total phenolic content (TPC) with 38.25 ±1.00 quercetin acid equivalent (QAE)/10 mg Dry Weight (DW) and 233.78 ±21.07 gallic acid equivalent (GAE)/10 mg Dry Weight respectivelly whereas lowest was recorded in V. infausta with 2.08 ±0.29 QAE/10 mg DW and G. flava with and 4.25 ±0.83 GAE/10 mg DW respectively. Higher 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2, 2'-Azino-Bis-3- Ethylbenzothiazoline-6-Sulfonic Acid (ABTS) activity was observed in methanolic extract of X. caffra (91.44 ±44 QAE/10 mg DW and 67.16 ±0.95 AAE/10 mg DW respectively) whereas the lowest was recorded in ethanolic extract of G. flava and distilled water extract of G. bicolor (13.40 ±0.86 QAE/10 mg DW and 2.78 ±0.50 AAE/10mg DW respectively). For antimicrobial activity, X. americana, X. caffra and M. zeyheri extracts displayed antibacterial action against Staphylococcus aureus and Escherichia coli when tested using the well diffusion method and mimimum inhibitory concentration respectively whereas no antifungal activity was recorded for the three methanolic extracts. Pearson correlations showed strong positive correlation for DPPH versus TFC, TPC and ABTS versus TFC, TPC, whereas TPC/TFC versus minimum concentration inhibition and zone of inhibition were strongly posititve and negative resepctively. The findings show the potential use of these fruit pulps for the development of functional ingredients with medicinal benefits.