Abstract: The applicability of microwave irradiation to assist the extraction of essential oil from Cyperus rotundus L. was investigated. The effects of extraction variables, especially solvent type, microwave power, microwave irradiation time, material-solvent mass ratio, moisture content and particle size of materials on extraction efficiency were investigated using single factor test and orthogonal method. The optimum conditions are obtaine as follows: cyclohexane as solvent, material particle size 0.28 mm, extracting twice, microwave power 450:W, irradiation time 90 s, solvent-material mass ratio 6:1. The extracted solution was concentrated under vacuum to give crude essential oil which was dissolved in ethanol and frozen at -15℃ for 48:h. The solution was then separated centrifugally and filtered to get rid of impurities. The essential oil with yield of 1.24% and purity of 97.3% was then obtained after distilling the liquor under vacuum.

Key words: essential oil, microwave-assisted extraction, Cyperus rotundus L.