Broad-spectrum antimicrobial activity, chemical composition and mechanism of action of garlic (Allium sativum) extracts

In many cultures, garlic (Allium sativum) has a reputation as a therapeutic panacea. In this work, a range of plant pathogenic bacteria and fungi were inhibited by garlic bulb extracts that were obtained under various conditions. The conditions included different solvents (distilled water, methanol and ethanol), and water at different pH values (pH 3.0, 5.0, 7.0, 9.0 and 10.7). Water extraction produced the best antimicrobial activity, compared to methanol and ethanol, and the greatest activity was obtained by extraction under strongly acidic condition (pH 3.0). Subsequent analysis using HPLC and GC–MS revealed that the major active ingredients were 3-vinyl-1,2-dithiacyclohex-5-ene and 3-vinyl-1,2-dithiacyclohex-4-ene. In addition, changes observed in membrane permeability, protein leakage and by scanning electron microscopy suggested that the antimicrobial activity of garlic extracts may be due to destruction of the structural integrity of cell membranes, leading to cell death.