Abstract: Essential oils were extracted from whole plants of Origanum vulgare L. by three different extraction methods, steam distillation, simultaneous distillation extraction and microwave-assisted steam distillation, and their chemical components were separated and identified by GC-MS to investigate the effect of extraction methods on the yield, volatile composition and antibacterial compounds of essential oil. The antibacterial activities in vitro of three essential oils against the tested strains were evaluated by measuring minimum inhibitory concentration (MIC). All the extracted essential oils were found to contain alcohols, hydrocarbons, acids, aldehydes, ketones, esters and phenols, but in different quantities. The major volatile antibacterial compounds in them were cryophllene, beta- phellandrene, careen, cyclohexane and limonene.

Key words: Origanum vulgare L., steam distillation, simultaneous distillation extraction, microwave-assisted steam distillation, volatile compounds