Optimization of ultrasound-assisted extraction (UAE) of phenolic compounds from Crataegus pinnatifida leaves and evaluation of antioxidant activities of extracts

In this study, an accurate method using high pressure liquid chromatography (HPLC) has been established for the simultaneous determination of chlorogenic acid (CA), vitexin-4 ''-o-glucoside (VG), vitexin-2 ''-o-rhamnoside (VR), orientoside (ORT), rutin (RT), vitexin (VIT) and hyperoside (HYP) from Crataegus pinnatifida leaves. The Box-Behnken design (BBD) combined with response surface methodology (RSM) was used to optimize the ultrasound-assisted extraction (UAE) method. Under optimized conditions (extraction temperature 41 degrees C, extraction time 31 min, ratio of liquid/solid 15 and ethanol concentration 39%), the yields of CA, VG, VR, ORT, RT, VIT and HYP were 0.46, 0.38, 4.37, 0.033, 0.036, 0.30 and 1.19, mg g(-1), respectively. Additionally, antioxidant activities of UAE extracts in DPPH radical scavenging (DPPH), ABTS radical scavenging (ABTS) and reducing power tests were determined as 0.69 mg mL(-1) (IC50 value), 0.86 mM Trolox and 0.24 mg mL(-1) (IC50 value), respectively. Compared with conventional maceration extraction (ME) and heat-refluxing extraction (HRE) methods, the UAE method showed remarkable advantages in terms of higher extraction yields and better antioxidant activities. Overall, the present results showed that UAE was an efficient and alternative method for the extraction of phenolic compounds from C. pinnatifida leaves and its extracts were potential antioxidant ingredients or additives for the food industry with potential preservation properties.