In vitro Antibacterial and Antitubercular Activities of Leaf Extracts of Senna occidentalis

Abstract

Aim: This study aimed to evaluate the antibacterial and antitubercular activities of ethylacetate and ethanol leaf extracts of Senna occidentalis. Study Design: Fresh leaves of Senna occidentalis collected from Suleja, Niger state were used for this study against some medically important micro-organisms viz; Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa, Salmonella paratyphi, Klebsiella pneumoniae, Mycobacterium bovis and Mycobacterium smegmatis. Place and Duration of Study: The study was conducted in Abuja, Nigeria at the Department of Microbiology and Biotechnology, National Institute for Pharmaceutical Research and Development [NIPRD], from February 2019 to April 2019. Methodology: Senna occidentalis leaves were extracted successively with ethyl-acetate and ethanol. The obtained extracts were tested in vitro for antibacterial activity by agar well diffusion method, while anti-tubercular screening was carried out by broth micro-dilution method. A fixed-dose concentration of chloramphenicol was used as a control drug against the bacterial isolates while isoniazid was used as control drug against the mycobacterium isolates. Results: The in vitro antibacterial screening showed that the crude extracts exhibited varying activity against the different microbes with highest zone of inhibition at 12 mm, and anti-tubercular activity with MICs ranging from 97.6-390.6 μg/mL.  Among these extracts, ethyl-acetate extract showed significant antibacterial activity against most of the test micro-organisms. The most susceptible micro-organism was P. aeruginosa (12mm zone in ethyl-acetate at 80 mg/mL) followed by B. subtilis (10 mm zone in ethyl-acetate extract at 80 mg/mL) and E. coli (9 mm zone in ethyl-acetate extract at 80 mg/mL). The ethanol extract was the most effective in inhibiting the growth of M. smegmatis and M. bovis with MICs of 97.6 μg/mL and 195.3 μg/mL. Conclusion: The activities observed could be attributed to the presence of some active metabolites contained in the extracts which could be useful in drug development for therapeutic purposes.