Sweet bay (Laurus nobilis L.) essential oil and its chemical composition, antioxidant activity and leaf micromorphology under different extraction methods

This research explored the essential oil (EO) of Laurus nobilis. Various parameters were recorded, including the amount of yield, chemical composition and antioxidant activity. The EO was obtained by hydro-distillation (HD), hydro-steam distillation (HSD), microwave-assisted hydrodistillation (MAHD), and ohmic-assisted hydrodistillation (OAHD). The micromorphology of the plant leaves were studied under the different extraction methods. The yields of EOs obtained by the mentioned extraction methods were 1.40, 0.74, 1.00 and 0.83 (% w/w), respectively. The main chemical components in EOs obtained by these methods were eucalyptol (34.4-50.0%), alpha-terpinenyl acetate (14.9-18.8%), terpinene-4-ol (4.7-6.0%) and sabinene (4.9-5.9%). Two of the extraction methods, i.e. OAHD and MAHD, yielded EOs that contained higher proportions of eucalyptol. SEM images of the leaves were taken after extraction. It was observed that the MAHD method had the most destructive effect on secretory cells, while the HSD method failed to damage numerous cells in the leaves. Generally, the results suggest that MAHD and OAHD can be recognized as clean and faster methods because of their shorter processing time and less energy requirements. The HD and HSD methods extracted EOs with more sesquiterpenes, while the MAHD and OAHD methods yielded higher amounts of oxygenated monoterpenes in the EO.