Insight into the essential oil isolation from Foeniculum vulgare Mill. fruits using double-condensed microwave-assisted hydrodistillation and evaluation of its antioxidant, antifungal and cytotoxic activity

As the increasing concern on the difficult environmental compatibility caused by traditional essential oil separation process, the development of efficient, rapid and environmentally friendly technique has become a major challenge. Furthermore, insight into the separation procedure of essential oils using fitting model is also an important problem for its industrial application. Thus in this work, the double-condensed microwave-assisted hydrodistillation (DCMHD) process of essential oils from commercially important natural plant fennel (Foeniculum vulgare Mill.) fruits was investigated systematically, including kinetic curves and essential oil compositions under different conditions, and response surface methodology (model fitting, ANOVA evaluation, diagnostics of polynomial model adequacy and response surface analysis). As compared with the second-order kinetic model, the first-order kinetic model appeared to be more suitable to fit the experimental data and interpret the mechanism. The yield of essential oil of 2.82 +/- 0.09 % was achieved under the optimum conditions, which was 1.10 times higher than that from hydrodistillation of 6 h. Additionally, the fennel essential oils obtained were analyzed to contain high proportion of trans-anethole (88.28 %) and oxygenated components (95.95 %), which contributed to the higher antioxidant, antifungal and cytotoxic activity. Overall, insight into the DCMHD process and biological activity of fennel essential oils provides a theoretical basis for the efficient separation of essential oils and the full utilization of natural aromatic plants.