Comparative Antibacterial Activity of Methanolic, Ethanolic and Aqueous Extract of Garcinia kola (Bitter kola) and Cola nitida (Kola nut)

摘要

Alternative herbal medicine has been used for centuries to treat various infections. Natural plants contain phytochemical properties similar to synthetic antibiotics. Due to multiple and repeated issues with antibiotic efficacy, it has become essential to evaluate biological properties of plants from different geographical origins. A comparative antibacterial activity of metanolic, ethanolic and aqueous extracts of Garcinia kola (bitter kola) and Cola nitida (Kola nut) were carried out against some test organisms (Salmonella species, Escherichia coli , Shigella species and Pseudomonas species). Agar well diffusion method was used in determining the antibacterial activity of the plant parts at different concentrations (100%, 75%, 50%, 25% and 12.5%) using methanolic, ethanolic and aqueous extracts of the samples. The results showed that the antibacterial activity of G. kola extract on the test organisms was significant for E. coli (p-values of 0.005); for Salmonella and Pseudomonas spp respectively (p-value of 0.001) and for Shigella spp (p-value of 0.016). For C. nitida , three bacterial isolates (Salmonella species, Shigella species and Pseudomonas species) were significantly inhibited having P-values of 0.000 for Salmonella and Pseudomonas respectively and p-value of 0.001 for Shigella species; however, E. coli was not significantly inhibited by C. nitida extracts (p-value of 0.203). Methanol extracts of the studied plants showed a wider spectrum of activity than ethanol and aqueous extracts. This study revealed the importance of these plant parts as a novel source of antimicrobial agents due to the increasing drug resistance among microorganisms. The infused extracts from the plants can therefore be considered by pharmaceutical industries in the production of cheap, affordable and available drugs for the cure of infections caused by these organisms in situations where expensive conventional drugs are unaffordable.