Evaluation of antibacterial and synergistic effects of Vernonia amygdalina and Ocimum gratissimum against selected bacteria

Abstract

Ocimum gratissimum L. (scent leaf) and Vernonia amygdalina L. (bitter leaf) are traditionally used as bacterial infection control agents and can be combined for effective activity. This study determined antibacterial and synergistic effects of both plants on six clinical bacterial isolates (Bacillus subtilis, Streptococcus sp., Staphylococcus aureus, Salmonella sp., Pseudomonas sp., and Escherichia coli).
Phytochemicals of O. gratissimum and V. amygdalina leaves were determined using standard methods. Ethanol, ethyl acetate, and water were used to extract phytochemical constituents of plants. Antibacterial activities were carried out using agar well diffusion method. Synergistic potency of leaves extracts was determined by combining V. amygdalina and O. gratissimum leaves extracts in ratio
50:50, 75:25 or 25:75. Phytochemical screening revealed the presence of alkaloids, saponins, tannins, flavonoids, and steroids. Antagonistic activity of extracts compared well with those of standard antibiotics. The mean zones of inhibition exhibited by ethyl acetate extract of V. amygdalina were 21±1.202, 20±0.333, 19±1.202, and 18±0.882 mm while those of O. gratissimum were 20±0.333,
18±0.882, 17±0.577, and 17±0.667 mm against B. subtilis, S. aureus, Pseudomonas sp., and Streptococcus sp., respectively. The synergistic activities were higher (25 - 26 mm) against B. subtilis, Streptococcus sp., and S. aureus at ratio 50:50. The synergistic effects of these plants could be harnessed for the development of a new antibacterial agent against antibiotic-resistant bacterial pathogens,
thereby contributing to the advancement of public health initiatives.