Abstract:

In the present study, we optimized the microwave-assisted diethyl ether extraction process of essential oil from the stems and leaves of fenugreek using single factor and orthogonal array design methods. In addition, reducing power, DPPH radical scavenging and Rancimat assays were used to see whether the extracted oil has antioxidant effect. The optimal extraction conditions were found to be: microwave power, low fire; length of extraction time, 30 s; solid/liquid ratio (g/mL), 1:4; and length of pre-extraction soaking time, 20 min. An oil yield of 3.374% was obtained under such conditions. Solid/liquid ratio had the most important effect on oil yield, followed by length of pre-extraction soaking time, microwave power and length of extraction time in decreasing order. The extracted oil had strong reducing power and DPPH radical scavenging activity and presented the highest protective effect against lipid peroxidation in lard at a concentration of 200 mg/L, which, however, smaller than that of vitamin C at the same concentration.

Key words: the stems and leaves of fenugreek, essential oil, microwave-assisted extraction, process optimization, antioxidant activity