Antibacterial and synergistic potency of methanolic leaf extract of Ocimum gratissimum L. and Vernonia amygdalina L.

Vernonia amygdalina and Ocimum gratissimum are common perennial shrubs that are used as vegetables and spices. Studies have indicated that both plants have several medicinal properties. This study investigated the antibacterial and synergistic potency of methanolic leaf extracts of Vernonia amygdalina and Ocimum gratissimum. The leaf samples were shade dried, extracted using methanol and tested against some bacterial isolates using agar well diffusion method. The mean zone of inhibition against E. coli, Staphylococcus aureus and Bacillus sp. was 13.67 mm, 13.33 mm and 13.00 mm, respectively by V. amygdalina, 13.00 mm, 12.67 mm and 13.00 mm, respectively by O. gratissimum, and 15.00 mm, 13.67 mm, 13.33 mm, respectively for synergy of V. amygdalina and O. gratissimum at 100% concentration. There was no significant variation (p > 0.05) among the various isolates, and plants and its combinations at 100% and 85% concentrations, but significant difference (p < 0.05) exists at 95% and 90% extracts. The findings showed that the combination had slight superior potency against the tested isolates.