Antimicrobial Activities of Extracts of Ginger and Garlic on Some Selected Bacterial Pathogens

Abstract

The rising incidence of antibiotic resistance has heightened the quest for alternative and supplementary antimicrobial agents, especially those originating from medicinal plants and dietary spices. Ginger (Zingiber officinale) and garlic (Allium sativum) contain bioactive phytochemicals, which have been proven to exhibit antibacterial activities. The investigation was conducted to determine the in-vitro antibacterial properties of aqueous and ethanolic extracts of ginger and garlic against some selected clinical bacterial pathogens viz. Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. The plant extracts were generated by water and ethanol extraction procedures and were analysed at different concentrations by disc diffusion and agar well diffusion methods. Inhibition zones were examined and the minimal inhibitory concentrations (MICs) were obtained at the values of 100, 50, 25, 12.5 and 6.25 mg/mL. Both ginger and garlic extracts showed concentration dependent antibacterial activity although the degree of inhibition was depending on the plant, extraction solvent, bacterial type and concentration. The highest zones of inhibition against S. aureus (31.0 ± 1.8 mm) and P. aeruginosa (28.0 ± 1.8 mm) were seen with the ethanolic garlic extract using the disc diffusion method. Ethanolic ginger extract also showed considerable effectiveness with highest inhibition zone of 29.0 ± 1.8 mm against P. aeruginosa. The MIC of the ethanolic extracts was as low as 6.25 mg/mL for some of the species tested. The aqueous extract of ginger was required 50 mg/mL for the inhibition of P. aeruginosa, but the garlic extract showed MIC values of 6.25 mg/mL against S. aureus and E. coli and 12.5 mg/mL against P. aeruginosa. In general garlic showed more antibacterial activity than ginger, particularly when extracted with ethanol. The studied extracts were sensitive to different degrees against Gram-positive and Gram-negative bacteria. The results imply that ginger and garlic contain bioactive elements with potential in vitro antibacterial action. Further studies on phytochemical characterisation, standardised extraction processes, toxicity assessment, mechanistic investigations and in-vivo evaluation are needed to identify their potential application as sources of antimicrobial compounds