Phytochemistry and Antimicrobial Activity of Extracts from Medicinal Plants Tithonia diversifolia and Olea africana

Abstract

In an increasing search of new antimicrobial agent to cope with the microbial resistance to antibiotics, scientists are searching from different sources including plants. Plants extracts of the leaves of Tithonia diversifolia and Olea africana were obtained using different solvents. In-vitro antibacterial activity of dichloromethane, ethyl acetate and methanol extracts of Tithonia diversifolia and Olea africana were evaluated against Pseudomonas aeruginosa, staphylococcus aureus, Bacillus subtilis and Escherichia coli, using micro-broth diffusion method. Zones of inhibition at different concentrations were recorded in millimeters. Growth of test pathogens (Staphylococcus aureus) were inhibited by dichloromethane leaf extract of T. diversifolia at higher concentration of 25 mg/mL (18 mm zone of inhibition), followed by inhibition of 14 mm (Pseudomonas aeruginosa). E. coli was found to be least sensitive to different plants extracts of T. diversifolia. Pseudomonas aeruginosa was susceptible to methanol extracts of the leaves of O. africana at a concentration of 25 mg/mL (18 mm zone of inhibition) followed by E. coli with a zone of inhibition of 17 mm. Staphylococcus aureus growth was inhibited by ethyl acetate extracts of O. africanawith a zone of inhibition of 19.20 mm. Results of the phytochemical screening revealed the presence of tannins, terpenoids, saponins, phenols and flavanoids in dichloromethane, ethyl acetate and methanol extracts of T. diversifolia, While alkaloids, terpenoids, tannins and flavones were screened in O. africana extracts. The activity of the crude extract was found to be concentration dependent on all the organisms tested. The occurrence of these phytochemicals in the selected plants of T. diversifolia and O. africana may justify their wide range usage in traditional medicine. However, other genera of Gram-positive and Gram-negative bacteria as well as fungi species should be tested in order to ascertain the broad spectrum activity of the crude extract.