Antioxidants and Antimicrobial- Activities of Methanol Leaf Extract of Senna occidentalis

Background: Oxidative stress and infectious disease have always been considered as a leading cause of morbidity and mortality in humans. Free radicals damage other molecules by extracting electrons from them in order to attain stability. The side effects associated with commonly used conventional antioxidants drugs have necessitated the search for natural antioxidants from plants extracts.

Objective: The antioxidants and antimicrobial activities of methanol leaf extract of S. occidentalis obtained from North Central, Nigeria were evaluated against some pathogenic microorganism.

Methods: The antioxidants activities were conducted using DPPH radical scavenging assay. The antibacterial activities were screened against Escherichia coli, Klebsiella pneumoniae and Candida albicans, Staphylococcus aureus, Pseudimonas aeruginosa and Salmonella typhi using agar well diffusion method at various concentrations (80-360 mg/ml). The minimum inhibitory concentration (MIC) was determined using serial dilution method while minimum bacterialcidal concentration (MBC) by plating various dilution of extract.

Results: The extract show significant antibacterial activities with MIC in the range of 160 mg/ml- 280 mg/ml and MBC in range of 160 mg/ml – 320 mg/ml. The most sensitive organisms were S. aureus and P. aeruginosa while K. pneumonia show some degree of resistances compared to other organisms tested. However, the organisms were not sensitive to the extract at the dose of 80 and 120 mg/ml. The extracts and the standard antioxidant (Vitamin E) promoted an inhibition of DPPH radical with IC50 value of the extract (263.53±3.24 mg/mL) significantly (p < 0.05) higher than 83.63±2.78 mg/mL obtained for standard drug.

Conclusion: Methanol leaf extract of S. occidentalis contains some useful potential antimicrobial and antioxidant compounds that could serve as candidate for the development of drug for therapeutic purposes.