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Chinese quince fruit is rich in proanthocyanidins (PAs), which have antioxidant properties. This work describes a method to isolate PAs from Chinese quince fruits by a combination of ball-milling pretreatment and enzyme-assisted extraction. Untreated PA fractions (UMP), ball mill pretreated PA fractions (BMP) and enzymatically hydrolysed PA fractions (BEP-1, BEP-2, BEP-3, BEP-4) were obtained. The total PA and total phenolic contents, antioxidant activity and α-amylase inhibitory activity of the six PA samples were determined, and their structural characteristics were also analyzed. BEP and BMP fractions were structurally similar with UMP, but had more total phenolics and PAs, and had higher antioxidant activities, lower thermal stability, and lower average molecular weight. Among them, BEP-4 was the most outstanding. Its total phenolics and PAs were 750.98 ± 6.95 and 948.72 ± 3.50 mg/g extract per gram dry weight, respectively. Its DPPH, ABTS, hydroxyl radical scavenging ability, and α-amylase inhibitory capacity had maximum values of 90.38%, 98.99%, 97.89%, and 92.98%, respectively. These investigations provide a new, efficient way to isolate proanthocyanidins from Chinese quince fruits, and reveal that Chinese quince fruits may be a good source of antioxidants, worthy of further development.

Chinese quince fruits are rich in proanthocyanidins (PAs), which have antioxidant properties. This work describes a method to isolate PAs from Chinese quince fruits by a combination of ball-milling and enzyme hydrolysis pretreatments. The yield, total PA and total phenolic contents, structural characteristics, antioxidant activity, and α-amylase inhibitory activity of different pretreated PA samples were determined and analyzed. Among them, the ball-milling combined with multi-enzyme (cellulase, xylanase, and pectinase) hydrolysis pretreated sample (BEP-4) was the most outstanding. The yield of BEP-4 could be improved up to 7.72%, which was 2.51 times higher than that of the conventional organic solvent extraction method (3.02%). It had the highest total phenols and PAs content of 750.98 ± 6.95 and 948.72 ± 3.50 mg/g extract, respectively. The thermal stability and molecular weight (9610 Da) of BEP-4 were lower than other fractions. BEP-4 contained a high proportion of PC structure (98.35%) and flavan-3-ol content (87.88%). It also had the highest antioxidant capacity with IC 50 values of 131. 45 ± 0.97, 22.66 ± 0.32, 134.05 ± 0.71, and 182.07 ± 0.28 μg/mL for DPPH, ABTS, hydroxyl radical scavenging capacity, and α-amylase inhibiting capacity, respectively. These investigations provide a new, efficient way to isolate PAs from Chinese quince fruits, and reveal that Chinese quince fruits may be a good source of antioxidants, worthy of further development.