Phytochemical screening and antibacterial activities of Ocimum gratissimum against some clinical isolates

Ocimum gratissimum is a common plant in the tropics and has been used in food and medicine. Its usage in food and medicine could be attributed to its phytochemical and antimicrobial properties. In this study the phytochemical and antibacterial attributes of aqueous and ethanolic extracts of O. gratissimum leaves was investigated against some selected clinical isolates. Susceptibility effects of these extracts were determined by agar well diffusion method against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Staphylococcus aureus. Phytochemical compounds such as alkaloids, saponins, phenol, phytates, oxalate, glycosides, and tannins were detected in O. gratissimum leaf extract. The antibacterial results showed that the efficacy of the aqueous extracts was more pronounced against the test bacterial, especially K. pneumoniae at minimum inhibitory concentration (MIC) of 0.2 mg/mL. The ethanol extract was more pronounced against S. aureus with diameter of zones of inhibition ranging from 12.84±0.01 – 19.15±0.02 mm at concentrations of 0.2 – 0.8 mg/mL respectively. The significant antibacterial properties of the leaf extract could be attributed to the presence of these bioactive compounds. Thus, this investigation proves to an extent that the O. gratissimum extracts when used against microorganisms has sufficient antimicrobial property.