Abstract: In this study,limonin was extracted from dried lemon peel by ultrasonic-assisted aqueous two-phase system of ethanol-(NH₄)₂SO₄. The effects of ethanol concentration, solid-liquid ratio,amount of ammonium sulfate,ultrasonic treatment temperature,ultrasonic treatment time,extraction temperature and extraction time,on the extraction yield,were studied by the single factor experiments and orthogonal tests.The results showed that when the volume concentration of alcohol was 60%,the solid-liquid ratio was 1:20 g/mL,the amount of ammonium sulfate was 12 g,the treatment temperature was 60 ℃,the ultrasonic treatment time was 30 min,the extraction temperature was 50 ℃ and the extraction time was 3 h,the extraction yield of limonin reached the maximum.Under the optimal conditions,three parallel experiments were carried out and the average extraction yield reached 0.3222%.The reproducibility of the optimized method was good.

Key words: aqueous two-phase system, ultrasonic, limonin, lemon peel, orthogonal test