Antimicrobial efficacy and phytochemical screening of aqueous and ethanolic extracts of Ocimum gratissimum (scent leaf) leaf against some clinical isolates

Abstract

Medicinal and aromatic plants form a numerically large group of economically important plants which provide basic raw materials for medicines, perfumes, flavours and cosmetics in Nigeria. This study investigated the antimicrobial activity of scent leaves (Ocimum gratissimum) extracts on four pathogenic microorganisms using the agar well diffusion method. These bacteria include; Pseudomonas aeruginosa, Salmonella typhi, Candida albicans, and Escherichia coli. Two different extracts were obtained from the plant samples (water-soluble and ethanol-soluble extracts). Both extracts showed the presence of some important phytochemicals, however screening of the ethanolic extracts showed that it contained high levels of saponin, tannins, phenolics, steroids and glycosides when compared with the aqueous extract. There were zones of inhibitions observed around the wells of both water and ethanol extract of Ocimum gratissimum. The results showed that the isolates behaved differently in their sensitivity to different extracts added to their growth medium ranging between 3 ± 0.01 – 35 ± 0.02 mm for ethanolic extract and 6 ± 0.02 – 45 ± 0.12 mm for the aqueous extract with significance (p < 0.05). Ethanol extract was strongly effective against the four clinical pathogens. The MIC, MBC and MFC test showed that the ethanolic and aqueous extract of the plants are bactericidal and fungicidal but their fungicidal activities are lower when compared with their bactericidal activities. This investigation indicates that Ocimum gratissimum had antimicrobial effect thus confirming its use in traditional medicine.