Antibacterial, anti-inflammatory and antimalarial activities of some Nigerian medicinal plants

Petroleum ether, dichloromethane and 80% ethanol extracts of 15 plant species from Nigeria were screened for in vitro antibacterial, anti-inflammatory and antimalarial activities. Antibacterial activity was tested using agar diffusion and microtitre serial dilution tests. Most antibacterial activity was against Gram-positive bacteria, with Staphylococcus aureus being the most susceptible of the bacteria tested. The highest activity was found in both petroleum ether and dichloromethane extracts of Mallotus oppositifolius leaves, petroleum ether, dichloromethane and ethanolic extracts of Newbouldia laevis roots, and ethanolic extracts of Morinda lucida and Canthium subcordatum roots. Against the Gram-negative Escherichia coli, the highest activity was found in dichloromethane root extracts of Newbouldia laevis, ethanolic root extracts of Phyllanthus amarus, Mallotus oppositifolius and Canthium subcordatum. A total of 60 plant extracts was screened for antiplasmodial activity. A chloroquine sensitive strain of Plasmodium falciparum (D10) was used. In the assay, the parasite lactate dehydrogenase (pLDH) activity was used to measure parasite viability. Eleven extracts showed promising activity, with IC50 ranging from 2.5μg ml-1 to 13.8μg ml-1. Cyclooxygenase (COX-1 and COX-2) assays were used to test for antiinflammatory activity. All the plant species, except for two, showed anti-inflammatory activity, with activity mostly in petroleum ether and dichloromethane extracts.