Effects of ultrasonic‐microwave assisted extraction with green solvent on the chemical constituents, antioxidant, and hypolipidemic activities of Manchurian walnut oil

A fast and efficient extraction method, ultrasonic-microwave-assisted extraction (UMAE) with a new green solvent Dimethyl carbonate (DMC), was developed for the extraction of Manchurian walnut kernel oil (MWKO). Through Box–Behnken design and analysis, the optimum extraction conditions were obtained: extraction time 28 min, liquid–solid ratio 7 ml/g, irradiation power 400 w, and the maximum extraction yield was 59.30%, which was 1.85-fold and 1.24-fold to that of ultrasonic-assisted extraction and Soxhlet extraction. Gas chromatography–mass spectrometry analysis showed that the unsaturated fatty acid content of the MWKO extracted with all three solvents was higher than 90%. The MWKO possessed stronger antioxidant activity with the tests of DPPH free radical scavenging, ABTS free scavenging, and ferric ion reducing ability. The lipid-lowering activity of MWKO was tested, and it was found that MWKO extracted by UMAE-DMC significantly inhibited lipid accumulation in HepG2 cells. In conclusion, UMAE-DMC is a perfect extraction method for selective extracting seed oil from plants. Practical applications In the present study, compared with the traditional method SE and UAE, UMAE-DMC has the advantages of shorter extraction time, higher extraction efficiency, and lower energy consumption. UMAE-DMC is a green and alternative extraction method for selective extracting of seed oil from plants. In addition, the MWKO possesses higher nutritional value and should be used as special edible oil for human health.