Abstract: The extraction and purification method of sesquiterpene lactones from the root of Inula helenium L.was optimized.The tests of orthogonal array design ［L₉ (3⁴)］were performed to analyze the effect of single factors,namely ethanol concentration,extraction duration and times of extraction,on the extraction yield of isoalantolcatone and alantolactone.As the result,the optimal extraction conditions were found as follows:the dried roots of I.helenium were extracted by reflux with 95% ethanol in solid/liquid ratio of 1:10 (w/v) for 2 hrs.The optimized purification process of ethanol extract was achieved by a pressurized silica gel (100-200 mesh) column chromatography with diameter to height ratio of 1:2.The ratio of mixed sample to silica gel was 1:3 (w/w),the eluent composed of petroleum ether (30-60 ℃) and acetone (100:3,v/v),flowed at the rate of 35 mL/min.The extraction yield of the lactones under the optimal method was above 70%,and the purity was above 90%.

Key words: Isoalantolcatone, alantolactone, orthogonal array design, silica gel column chromatography, Inula helenium L.