Antimicrobial activity and chemical composition of Origanum glandulosum Desf. essential oil and extract obtained by microwave extraction: Comparison with hydrodistillation

Origanum glandulosum Desf. essential oils obtained by hydrodistillation (HD), solvent-free microwave extraction (SFME) and the extract obtained by microwave-assisted extraction (MAE) were investigated by capillary gas chromatography and gas chromatography/mass spectrometry. The main components of both oils obtained by HD and SFME were thymol (41.6–81.1%) followed by γ-terpinene (27.0–3.1%), p-cymene (17.1–4.0%) and carvacrol (2.2–4.4%), respectively. In the same way, thymol (65.4%), γ-terpinene (13.1%), p-cymene (7.2%) and carvacrol (3.5%) were the main components of the extract obtained by hexane microwave extraction. The SFME method was most selective for the extraction of thymol. The examination of the antimicrobial activity of both essential oils against 10 bacteria, two yeasts and four moulds revealed that O. glandulosum oil is more antifungal than antibacterial. To our knowledge, the antifungal activity of the O. glandulosum oil obtained by HD and both antimicrobial and antifungal activities of O. glandulosum SFME oil were not yet reported. Our study suggests that O. glandulosum essential oil has the potential to be used as a food preservative and to prevent the growth of nosocomial bacteria.