Phytochemical Composition and Antibacterial Activities of the Ethyl Acetate Leaf Extract of Ocimum basilicum

Abstract

IntroductionAntibiotic resistance is a serious threat to humankind. There is need for the development of new therapeutic options. Ocimum basilicum has been used traditionally as a medicinal herb against infectious diseases and as a food additive. ObjectiveThis study aimed at evaluating the phytochemical composition and in vitro antibacterial activities of the ethyl acetate leaf extract of Ocimum basilicum. MethodsOcimum basilicum leaves were collected from Mbeere, Embu County, Kenya and ethyl acetate extraction done at Kenyatta University. Phytochemical composition was evaluated by Gas chromatograph mass spectrophotometry while antibacterial activities were evaluated by disc diffusion and broth microdilution methods. The test microorganisms were methicillin resistant S. aureus, S. aureus, P. aeruginosa and E. coli. ResultsThe extract exhibited a broad spectrum antibacterial activity. The gram negative bacteria showed more susceptibility to the organic extract compared to the gram positive bacteria. Pseudomonas aeruginosa had the highest zone of inhibition (27.00 ± 2.00 mm), while the S. aureus isolate had the lowest zone of inhibition (24.00 ± 1.00 mm). Escherichia coli, S. aureus and MRSA species had an MIC of 62.5 mg/ml compared to P. aeruginosa with an MIC of 125mg/ml when exposed to the leaf extract. The antibacterial activity could be attributed to the synergistic effects of phytochemicals such as terpenoids, alkaloids, essential oils, fatty acids, flavonoids and aldehydes that have been known to have antimicrobial properties. A total of 30 phytochemical compounds were eluted from the extract of O. basilicum. Nootkatone, a sesquiterpenoid had the highest concentration at 20.86mg/g. The compound 1,3-Dimethyl-5-isobutylcyclohexane, a fatty acid had the lowest concentration at 0.10mg/g. ConclusionO. basilicum has antibacterial activities on the tested pathogens and can be used to treat infections. Phytochemicals with antibacterial effects in the herb can be used as lead molecules in developing new antibacterial drugs.