Phytochemical Screening and Antibacterial Activity of the Crude Extract of Scent Leaf (Ocimum gratissimum) on Escherichia coli and Staphylococcus aureus

Abstract

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.