Optimization of ultrasound-assisted aqueous two phase extraction of polyphenols from olive leaves

In this study, polyphenols from olive leaves was extracted by ultrasound-assisted aqueous two phase extraction (UAATPE). Based on single factor experiment and response surface methodology (RSM), the optimum extraction conditions of polyphenols contained 29% (w/w) (NH₄)₂SO₄, 35% (w/w) ethanol, pH 6.7, and 45 °C. The maximum extraction yield of polyphenols and oleuropein content were 34.06 mg/g and 44.13 mg/L, respectively. Compared with ultrasound-assisted extraction (UAE) and aqueous two phase extraction (ATPE), the extraction yield of polyphenols by UAATPE was 9.48 and 61.19% higher, respectively. In addition, the extract of UAATPE had higher purity. The results of antioxidant activity showed that polyphenols extracted by UAATPE had stronger DPPH and hydroxyl radicals scavenging ability and reducing power. Therefore, UAATPE is an efficient method for extracting polyphenols from olive leaves.