In this study the effect of distillation and solvent extraction methods were studied on many factors; oil percentage, physical and chemical properties, and percentage of decay of both Australian (white and red) and Chinese garlic. On the other hand, the antimicrobial effect of Australian and Chinese garlic plants was determined at various concentrations against Staphylococcus aureus ATCC®25923, Pseudomonas aeruginosa ATCC®9027, Escherichia coli ATCC®25922 and Bacillus subtilis ATCC®6633. Furthermore, the antimicrobial effect of Australian and Chinese garlic plants was compared with that of the antibiotics at definite minimum inhibitory concentrations. The highest percentage of extracted oil was obtained from the white Australian garlic followed by the red one. The solvent extraction method showed higher efficiency in oil extraction than the distillation method. Moreover, the white Australian garlic was found to have the best physical and chemical properties followed by the red one. It is worth mentioning that, the Chinese garlic  has higher resistance to decay more than the red Australian garlic. Therefore, it is recommended to use the white Australian garlic due to its high oil content which has potential antibacterial activity and has the best physical and chemical properties, but it should not be stored to prevent loss on decay. 

 

Key words: Antimicrobial activity, distillation, oil extraction, synergistic effect.