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Antimicrobial and Phytochemical Screening of some Zimbabwean Medicinal Plants

Munodawafa, Tafadzwa, Chagonda, Lameck Shoriwa, Moyo, Sylvester Rodgers
Journal of Biologically Active Products from Nature 2013 v.3 no.5-6 pp. 323-330
Aspergillus niger, Candida albicans, Erythrina abyssinica, Escherichia coli, Peltophorum africanum, Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus, Ximenia, Ziziphus, alkaloids, anthraquinones, antifungal properties, cardiac glycosides, coumarins, endangered species, flavonoids, freeze drying, medicinal plants, methanol, minimum inhibitory concentration, plant extracts, reference standards, saponins, screening, tannins, thin layer chromatography, wells, Zimbabwe
Twelve (12) medicinal plants endangered and commonly used by communities and traditional medical practitioners in 5 districts of Zimbabwe were selected. Twenty methanol freeze dried plant extracts were screened for phytochemistry using thin layer chromatography (TLC) with detection by UV and reagent sprays. Phytochemical group investigations indicated presence of tannins (80 %), saponins (70 %), flavonoids and cardiac glycosides (40 %), anthraquinone derivatives and coumarins (25 %) and alkaloid (15 %). Antibacterial and antifungal activity was tested by agar-well diffusion method using standard antimicrobial strains and expressed as average diameter of the zone of inhibition around the wells compared with reference standards. Most of the plant extracts were active against gram positive Staphylococcus aureus and Streptococcus Group A with Erythrina abyssinica, Ximenia caffra and Ziziphus mucronata being the most active. Extracts of Peltophorum africanum and Ximenia caffra were strongly active against gram-negative Escherichia coli and Pseudomonas aeruginosa. None of the extracts had pronounced activity against Candida albicans and Aspergillus niger. Dicoma anomala and Peltophorum africanum however, showed moderate activity against Candida albicans . Minimum inhibition concentrations (MICs) of active plant extracts ranged between 0.23 mg/ml to 5 mg/ml. The studies demonstrate the potential value of medicinal plants used by traditional medical practitioners and should be preserved, propagated and developed for the treatment of various ailments and for industrial expansion.