Influence of ultrasonic pretreatment on the extraction yield and chemical composition of oregano essential oil and its application to ozone-treated samples

The present study aimed to optimize and validate a method using ultrasonic pretreatment combined with hydrodistillation to achieve good yield and high concentrations of phenolic compounds (thymol and carvacrol) from Origanum vulgare L essential oil. The response surface methodology based on the Doehlert matrix domain was utilized for this purpose. The extraction method was optimized as a function of the ultrasound sonication time (0, 15, 30, 45, and 60 min) and dried oregano leaves mass (20, 35, and 50 g). The optimal condition found was 35 g of oregano and 30 minutes of sonication. Under these conditions, 0.47% oil yield, 123.5 g L⁻¹ of thymol, and 20.9 g L⁻¹ of carvacrol were obtained. The volatile constituents of the essential oil were identified by gas chromatography coupled to mass spectrometry. The method was validated, showing good selectivity, linearity (R 2 > 0.99), limit of detection and intra-day and inter-day precision. In a second phase, the validated method was used to analyze oregano samples exposed to ozone gas (10 mg L -1 ), a potent oxidizing agent used in food decontamination. A significant positive effect on carvacrol and thymol concentrations was observed after 48 h and 72 h of oregano exposure to ozone gas, respectively. • Ultrasonic pretreatment favored the extraction of Origanum vulgare essential oil • The method validated proved to be efficient, selective, and sensitive extraction method. • Validated method was applied to ozonated oregano samples • Ozone is a potential biotechnological tool to improve the quality of plant extracts.