Antibacterial Activity of Ocimum gratissimum (scent leaf) on Some Pathogenic Gastrointestinal Bacteria

The emergence of antibiotic resistance as well as the recent undesirable side effect of some of the
commercially available antibiotics has led to the screening of plant extract in order to discover new
drug that could serve as alternative therapy for the treatment of various infections and diseases.
Fresh leaf of Ocimum gratissimum (scent leaf) sample was collected, air-dried at room temperature
and blended to powder using electric blender. The extraction was done using reflux extraction method
and methanol as solvent. The phytochemical analysis and the antibacterial activity of O. gratissimum
were determined to ascertain the different phytochemicals present in the plant extract. The extract
was also tested against some selected Gram negative intestinal pathogenic bacteria; Escherichia coli,
Shigella and Salmonella species, by reconstituting the extract in dimethyl sulphoxide (DMSO) to
obtain different concentration (0.2, 0.1, 0.05 and 0.025 g/ml) and agar well diffusion techniques were
used to evaluate the antibacterial susceptibility of the leaf extract. The qualitative phytochemical
analysis of the extract revealed the presence of alkaloid, anthraquinone, flavonoid, glycoside, phenol,
saponin, steroid and tannins. The result of antibacterial analysis showed that the extract of O.
gratissimum has antibacterial activity against E. coli. This could be as a result of the presence of
various phytochemicals or the interaction of one or more of the identified metabolites against the test
organisms. However, there was no zone of inhibition (antibacterial effect) recorded on Salmonella and
Shigella spp. as they were resistant to the extract. The results obtained from this research, suggest
that Escherichia coli was susceptible to the leaf extract and the plant could be used as potential
source of natural product for the treatment of infection.