A modified approach for separating essential oil from the roots and rhizomes of Asarum heterotropoides var. mandshuricum

Abstract To efficiently separate essential oil from the roots and rhizomes of Asarum heterotropoides var. mandshuricum, a modified dynamic nitrogen-protected microwave-assisted hydrodistillation connected liquid-liquid extraction (DNMHDLLE) technique was developed. In addition to collect essential oil at the bottom of hydrosol in the conventional oil-water separation process, another extraction process was realized for extracting some essential oil components from the hydrosol using a small amount of organic solvents, which can significantly enhance the essential oil yield, effectively reduce the organic content in wastewater and its further disposal burden. The addition of glass beads as the packing in the second separation column had a positive influence on the essential oil yield. After the investigation using a single factor experiment and a response surface analysis, the optimum conditions were determined to be 28 min microwave irradiation time, 11 mL/g liquid-solid ratio, and 550 W microwave irradiation power. Under the optimum conditions, the yields of A. heterotropoides var. mandshuricum essential oil obtained in the first and second separation columns were 1.92 ± 0.07% and 0.50 ± 0.02%, respectively. Using GC-MS analysis, the essential oil containing oxy-compounds with a higher relative content was separated in the second separation column. In addition, the proposed method was compared with other techniques, including efficiency, environmental impact and economic effect, which indicated that the developed technique can effectively improve the essential oil yield, and take full advantage of raw material resources.