Effect of temperature on antibiotic properties of garlic (Allium sativum L.) and ginger (Zingiber officinale Rosc.)

Garlic and ginger are the two most common herbs used in traditional medicine practice for their antimicrobial activities. Moreover, in many countries, they are also used with boiled food preparations, which can destroy their important medicinal properties. We conducted an agar well diffusion assay with aqueous extracts of garlic and ginger to observe the effect of temperature on their antibiotic properties against three human pathogenic bacteria namely Klebsiella pneumoniae, Escherichia coli and Staphylococcus aureus. The results show that in general, garlic has significantly greater zone of inhibition (mean = 23.3 mm) than ginger (mean = 19.0 mm) at both, room temperature (26°C) (t = 4.91; α = 0.05; P < 0.01) and at higher temperature (100°C); garlic (mean = 15.6 mm); ginger (mean = 0 mm) (t = 17.76; df = 2; α = 0.05; P < 0.001). On observation, it was found that although higher temperature significantly reduced the antibacterial properties of both plants, nevertheless it affected ginger more (t = 32.9, df = 2; α = 0.05; P < 0.001) than garlic (t = 11.5, df = 2; α = 0.05; P < 0.01). From our study, we can conclude that garlic has more prevailing and sustainable antibiotic properties than ginger under normal and higher temperature regimes. We recommend that garlic not only has very promising potential for a broad-spectrum antibiotic drug against many pathogenic bacteria, but also significantly sustains its antibacterial property than ginger even with boiled food preparations. In addition, it can be used as an effective source of natural herbal antibiotics with or without boiling.