Comparative Study of Yield, Chemical Composition and Antioxidant Activity of Wild Algerian Lavandula stoechas L. Obtained by Ultrasound Pre-treatment and by Conventional Hydrodistillation

The paper presents research results concerning the influence of ultrasonic pre-treatment (time intervals of 10, 20, 30, 45, and 60 min) on the process of extraction of essential oils from wild Algerian Lavandula stoechas. Tests were carried out in two populations. A sonication pre-treatment time of 10 min followed by 90 min of hydrodistillation (US-HD) gives a yield of 1.60 ± 0.1% of Kodiat essential oils (KEO). This pre-treatment time proved to be the best when compared with other pretreatment times. However, overall best yield (1.03 ± 0.07%) of El-Kahla essential oils (EEO) was obtained at 60 min of pre-treatment. These yields are higher compared with those (0.64 ± 0.02% and 0.50 ± 0.02%) obtained after 180 min of only hydrodistillation (HD) for the two samples of Lavandula stoechas, respectively. About 90.69% and 89.36% of total compounds were identified using chromatography–mass spectrometry (GC– MS) in KEO and EEO treated by ultrasound versus untreated samples (89.26% and 76%, respectively). A qualitative and quantitative difference in chemical composition between the essential oils of treated and untreated samples of the two harvesting sites was found. The percentage of most of the major compounds (fenchone, camphor, 1,8-cineole, bornylacetate, myrtenyl-acetate, and viridiflorol) and other compounds identified is higher in treated samples. GC/FID (flame ionization detector) analysis of KEO showed that the percentage of fenchone and camphor as major components is greater at 60 and 20 min of ultrasonic (US) pretreatment, respectively, compared with HD and the other US pre-treatment times. Results of the present study clearly indicated that sonication treatments are effective in enhancing the antioxidant activity of Lavandula stoechas extracts and could be further explored for commercial purposes to benefit consumers and the environment.