Efficacy of Pterocarpus angolensis crude extracts against Candida krusei, Staphylococcus aureus, Streptococcus agalactiae and Escherichia coli

BACKGROUND: The medicinal plants used to treat different ailments in Malawi contain important phytochemicals which have bactericidal and anti-fungal properties. Pterocarpus angolensis, locally known as mlombwa tree, which is found in many parts of Malawi, is one such a plant and was studied. AIMS: In vitro analysis of the antimicrobial properties of Pterocarpus angolensis crude extracts on Staphylococcus aureus, Escherichia coli, Streptococcus agalactiae, Candida krusei and determination of the phytochemicals there in. METHODS: In this study, different organs of P. angolensis, a medicinal plant which is locally used to treat skin diseases, were qualitatively screened for the presence of phytochemical constituents and quantitatively assayed for the antimicrobial activity to ascertain their pharmaceutical potential. The aqueous, dichloromethane and methanolic extracts of the leaves, stem-bark, fruits and roots of the plant were tested against Escherichia coli, Staphylococcus aureus, Streptococcus agalactiae and Candida krusei by the macro tube dilution method. These pathogens were selected due to their significant contribution to infectious disease burden of most hospitals and also the fact that of late, they have shown signs of resistance to conventional antibiotics. RESULTS: The study revealed that P. angolensis contained tannins, flavonoids, saponins and terpenoids. All the extracts exhibited some antimicrobial activity against the test organisms. However, the activity of the extracts depended on concentration and microbial species. The minimum inhibition concentration (MIC) values of the extracts ranged from 0.166 g/ml to 0.01046 g/ml with the dichloromethane and methanolic extracts exhibiting more activity than the aqueous extracts. The minimum bactericidal concentration and minimum fungicidal concentration (MBC and MFC respectively) values of the extracts ranged from 0.166 g/ml to 0.0417 g/ml. CONCLUSION: The results obtained indicate that Pterocarpus angolensis has both antibacterial and antifungal properties and could be used for the treatment of Taenia capitis (ring worm) and other ailments. Use of the isolated and purified compounds from P. angolensis could increase the susceptibility of the tested pathogenic microorganisms in this study.