PHYTOCHEMICAL SCREENING, ANTIOXIDANT AND HEAVY METAL ANALYSIS OF MEDICINAL PLANTS SOLD BY STREET VENDORS IN GABORONE, BOTSWANA

The aim of this study was to screen for the various medicinally important phyto-active compounds and investigate the total phenolic content, free radical scavenging activity and heavy metal content of three herbal formulations [Motsosa (believed to be treat erectile dysfunction); Thatswamadi (believed to remove toxins from blood and alleviate fatigue), and HBP(believed to alleviate discomfort associated with increased blood pressure)] sold by street vendors in Gaborone. Qualitative phytochemical analysis revealed presence of saponins, flavonoids, phytosterols, steroids, phenols, cardiac glycosides and terpenoids. There is strong evidence from the literature that these phytochemicals play a role as health improving remedies. All samples were obtained from local traditional healers and extracted by cold maceration in methanol for five days with periodic vigorous agitation. Total phenolic contents (TPC) measured by Folin-Ciocalteu varied from 1231.3 to 752.4mg/l GAE. The order TPC was HBP>Thatswamadi>Motsosa. The antioxidant activity as determined by the DPPH radical scavenging assay, revealed that, at all tested concentrations, HBP and Thatswamadi showed equal scavenging potencies (90%) similar to control Quercetin, whilst Motsosa exhibited lower than 60% scavenging power. Heavy metal analysis by Flame Atomic Absorption Spectroscopy showed non-detectable levels of Nickel, Copper, Cadmium, Lead, and Chromium. This work has validated the use of these formulations as health improving remedies. However, analysis of microbial contamination and structural elucidation of bioactive constituents should be carried out.

Keywords: antioxidant activity, phytochemical screening, heavy metals, Botswana Herbs.