Antioxidant Activity and Total Phenolic Contents of some Traditional Medicinal Plants from Zimbabwe

Abstract

Fourteen (14) medicinal plants used by traditional medical practitioners in treating sexually transmitted diseases and common ailments were selected after an ethno-botanical survey of five districts from Zimbabwe. Plant extracts were screened for phytochemical composition, antioxidant activity by reducing 2,2-diphenyl-picrylhydrazyl (DPPH) free radical with ®-carotene as reference and through total phenolic content (TPC) by Folin-Ciocalteu reagent using gallic acid as reference. Ten (10) of the twenty-eight (28) methanolic extracts exhibited strong antioxidant activity with percentages equal or greater than 90 % compared to reference ®-carotene (99 %). Antioxidant activity for Rhus chirindensis, Khaya anthotheca, Gymnosporia senegalensis and Flacourtica indica was equal or greater than 95 %. Their TPCs ranged from 0.596 mg/mg to 0.105 mg/mg GAE. The TPC in some of the extracts correlate with their antiradical activity (r2=0.57) confirming that the phenolics are the likely cause of the radical scavenging activity. Commonest phytochemical groups identified were tannins, flavonoids and saponins. The strong antioxidant activity combined with potential antiinfective activity may reflect the popular use of these medicinal plants by traditional healers in treating viral, bacterial and fungal infections caused by HIV/AIDS, cancer, diabetes, cardiovascular diseases as well as other neurodegenerative diseases by arresting or reversing cellular damage caused by reactive oxygen species. Theplants could be sources of new therapeutic drugs and should be harvested sustainably, cultivated and propagated.