Effects of ultrasound pre-treatment on quantity and quality of essential oil of tarragon (Artemisia dracunculus L.) leaves

Hydro-distillation with ultrasound was used for extraction of essential oil of tarragon (Artemisia dracunculus L.) leaves. The results of this method were compared with a traditional distillation method considering the extraction kinetics as well as the physicochemical and antioxidant properties of the essential oil. The experiments were ran at three sound power levels (250, 350 and 500 W), three levels of sonication time (20, 30 and 40 min) as well as without sonication as a control in a completely randomized design with three replications. Gas chromatography was used to identify the essential oil compounds. Antioxidant properties were studied using the reducing DPPH radical method. The statistical results showed that the effect of ultrasound power on the essences extracted was not significant. The effect of sonication time on the essential oil content was significant at the 5% level. The highest amount of extracted oil was observed at the power of 500 W for 30 min while the lowest amount was found at 500W for 40 min. The highest percentage of estragole, which is the most important compound of tarragon was achieved with the proposed method. The highest antioxidant activity was for the extracted essential oil using ultrasound pre-treatment with 350 W power for 30 min and the control samples showed the lowest level.