Optimization of ultrasonic extraction process for lutein from pumpkin peel by response surface methodology

Ultrasonic wave was applied for extraction of lutein from pumpkin peel. First of all, the effects of main parameters including extraction solvent type, solvent volume ratio, ultrasonic power, liquid to solid ratio and extraction time on extraction yields of lutein and its cis isomers from pumpkin peel were studied. Based on the single factor experimental analysis, through the response surface, the optimization parameters were established. The results indicated that the ethanol petroleum ether(2:1, V/V)is the best solvent for the extraction of lutein pumpkin peel. One trans-lutein and four cis-isomers(15-cis lutein, 13/13'-cis lutein, 9-cis lutein, 9'-cis lutein)were identified in the extract of lutein from pumpkin peel. Furthermore, the optimum technological conditions were extraction solvent ratio of 2:1(ethanol/petroleum ether, v/v), liquid to solid ratio of 40:1 mL/g, ultrasonic power of 210 W and extraction time of 30 min. The yields of lutein and its cis isomers under the conditions were(229.7±9.1) μg/g dw and(9.4±0.2) μg/g dw, respectively, which was in good agreement with the predicted value. This study provided a reference for the efficient extraction of lutein and the comprehensive utilization of pumpkin peel.