Phytochemical and antibacterial activity of Ocimum gratissismum L. against three selected gastrointestinal tract pathogens

The rise in the incidence of side effects of many synthetic antimicrobial agents and prevalence of multidrug resistant bacteria has spurred scientists on the research for plant based antimicrobial of therapeutic potentials. Ocimum gratissimum L. presents such potential of high medicinal value. This plant is used in Nigeria traditionally as condiments and for treatment of various ailments. This study is aimed to determine the phytochemical and antimicrobial property of ethanol and aqueous extracts of O. gratissimum L. leaves. Phytochemical screening of the leave extracts confirmed the presence of Steroid, Tannins, Flavonoid, Terpenoid, Alkaloid, Saponin and Phlobatannis. Ethanol and aqueous extracts were obtained from the powdered leaves of O. gratissimum using ethanol and distilled water respectively. These were later filtered and the filtrates were concentrated in water bath at 50^oC. Mueller-Hinton agar was used for the antibacterial susceptibility using the agar well diffusion method. For ethanol extract, all the isolates were susceptible at 0.2g/mL, 0.1g/mL and 0.05g/mL concentrations. However, for aqueous extract, all the isolates were resistant at 0.05g/ml and 0.025g/ml but at 0.2g/ml concentration all the isolates were susceptible. Staphylococcus aureus was resistant at 0.1g/ml, except Pseudomonas aeruginosa and Bacillus cereus which were susceptible with a diameter 15mm, and 14mm respectively. Ciprofloxacin used as positive control also inhibited the growth of the bacterial isolates with the diameter of zone of 25mm. Results obtained from this study showed that the extracts of Ocimum gratissimum L. has antibacterial activities against the selected gastrointestinal tract pathogenic bacteria and also possess some bioactive compounds.