Proximate analysis and antibacterial effect of methanolic extract of the leaves of Ocimum gratissimum (Lamiaceae) against Streptococcus species and Pseudomonas aeruginosa

Abstract

Ocimum gratissimum (Lamiaceae) commonly called scent leaf is a herbaceous plant. It is indigenous to Africa and Southern Asia. Ethnomedically, it is known for its anti inflammatory, antipyretic and diaphoretic activity. The aim of this study is basically to evaluate the antimicrobial activity of the leaf of Ocimum gratissimum and to determine its phytochemical, physicochemical and chemomicroscopic properties. Evaluation of the chemomicroscopic, phytochemical and physicochemical profile was carried out using standard methods. The antimicrobial effect of the methanol extract of Ocimum gratissimum leaves was evaluated using sensitivity test and minimum inhibitory concentration. The phytochemical screening, revealed the presence of alkaloids, saponins, tannins, terpenes and flavonoids. The chemomicroscopy of the powdered leaf showed the presence of lignin, starch, cellulose and calcium oxalate. The physicochemical analysis revealed 8.5% moisture content, 6.5% total ash value, 0.45% acid insoluble ash value, 5.95% water soluble ash value, 35.2% alcohol soluble extractive value and 34.4% water soluble extractive value. The zones of inhibition of Pseudomonas aeruginosa and Streptococcus spp. were 10.33mm and 8.83 mm, respectively, at 200mg/ml with P. aeruginosa being the more susceptible. Both organisms have showed same minimum inhibitory concentration (MIC) of 12.5 mg/ml.