Structures and biological activities of proanthocyanidins obtained from chinese quince by optimized subcritical water-ethanol extraction

Subcritical water-ethanol extraction (SWE) was performed to extract proanthocyanidins (PAs) from Chinese quince fruits. The extraction parameters (temperature, time, liquid-solid ratio) were optimized using response surface methodology (RSM), based on single-factor experiments. The optimal SWE conditions were: temperature, 135 °C; time, 31 min; liquid-solid ratio, 32 mL/g. The maximum PAs obtained were 22.36 ± 0.35 mg PB2/g DW, which matched predicted values. In the analysis of PAs, 7 compounds were identified: catechin, epicatechin, epicatechin gallate, epigallocatechin-3-gallate, and proanthocyanidins dimers, trimers and tetramers. Structurally, these PAs contained substantial procyanidin (PC) but little prodelphinidin (PD). The findings revealed that SWE yielded more total PA than the conventional method extraction (CME). Furthermore, compared with CME PAs, PAs obtained by SWE showed higher radical scavenging capacities (IC 50 : 139.32 µg/mL for DPPH; IC 50 : 113.11 µg/mL for ABTS) and stronger α-amylase inhibition (IC 50 : 88.29 µg/mL). These results indicate that SWE is an efficient method for the separation of PAs from Chinese quince. Chinese quince PAs represent a potentially valuable resource for use in functional foods and nutraceuticals.