Scent (Ocimum gratissimum) leaves are known for their medicinal values for a long. The study was carried out on phytochemical screening and antibacterial activity of scent leaf extracts on E. coli and S. aureus. Antibacterial assay of the plant extracts was carried out on the test isolates, by inoculation on the surface of freshly gelled sterile nutrient agar plates by streaking using sterilized swab stick and the potent extracts was determined according to the macro broth dilution technique. Phytochemical screening of O. gratissimum leaves revealed the presence of steroids, saponins, flavonoids, alkaloids, cardiac glycosides and tannins in all the extracts. There was decreased in antibacterial activity with decreased in concentration of the extract as the concentration of the extract decreases from 200 – 25 mg/ml, the zones of inhibition also decreased from 20 to 11 mm (ethanol extract) and 17 – 10 mm (aqueous extract) for S. aureus; 19 – 10 mm (ethanol extract) and 15 – 8 mm (aqueous extract) for E. coli. The Minimum Inhibitory Concentration (MIC) of O. gratissimum extracts against the selected clinical isolates revealed no growth (clear) in all the test organisms at the concentration of 200 mg/ml. Also, the Minimum Bactericidal Concentration (MBC) showed no growth of bacterial colonies at the concentration of 200 mg/ml. It was observed from the study that ethanol and aqueous extracts exhibited high inhibitory activities on Escherichia coli a representative of enteric coliforms and Gram negative bacteria and Staphylococcus aureus a representative of Gram positive bacteria. Ethanolic extract had higher inhibition compared to the aqueous extract. This can be deduced to the ability of ethanol to extract more of the essential oils and secondary plant metabolites which are believed to exert antibacterial activity on the test organisms.

It was reported in 2005 during WHO survey that about 70-80% of the world population use medicinal plants either in their crude unmodified form or partially in their modified semi-synthetic form of plant sources in their primary healthcare. The present study investigated the phytochemicals and antimicrobial activities of the leaf extracts of Cerathoteca sesamoides and Chromolaena odorata to ascertain their potentials in herbal medicine. Fresh leaf of the plants obtained from Lafia in Nasarawa State, Nigeria were dried, powdered, and subjected to methanolic extraction, partition, phytochemical, and antimicrobial analyses using standard methods. Partitions from n-hexane, methanol, ethyl acetate, chloroform, and residue extracts were tested against clinical bacteria Escherichia coli, Klebsiella spp., Pseudomonas aeruginosa, Staphylococcus aureus, and fungus Candida albicans. Among the four different solvents used in partitioning methanolic and ethyl acetate extracts of both plants contain flavonoids, tannins, alkaloids, terpenoids, saponins, steroids, and cardiac glycosides. Saponins were absent in the n-hexane and chloroform extracts of C. odorata and the ethyl acetate extract of C. sesamoides. While flavonoids were present in the n-hexane extracts of C. odorata, they were absent in C. sesamoides. Anthraquinone and reducing sugar were absent in all the solvent extracts of both medicinal plants. The antimicrobial susceptibility tests showed that n-hexane and residue extracts of both plants had no activity against the tested microorganisms. The chloroform and ethyl acetate extracts of C. sesamoides and C. odorata (at 12.5 mg/ml) were active against all the tested clinical bacteria K. spp., E. coli, P. aeruginosa, S. aureus, and C. albicans. The methanolic extracts of both plants were active against the bacterial isolates but inactive against C. albicans. The minimum bactericidal concentration of these plant extracts was ≥50 mg, while the minimum inhibition concentrations ranged between 12.5 mg and ≥50 mg. The findings showed that the chloroform or ethyl acetate extracts of the leaves of these plant drugs could be used to treat urinary tract infections.