Abstract:

This study aimed to address the bottleneck in the resource utilization of Hippophae rhamnoides Linn. pomace, optimize the extraction process, and investigate their antioxidant protective effects on HaCaT cells damaged by UVB irradiation. A “defatting-composite enzymatic hydrolysis-ultrasound synergistic” technique was adopted: After defatting Hippophae rhamnoides Linn. pomace with petroleum ether, a mixture of 2.5% pectinase and 2.5% cellulase was used to break the cell walls. Combined with 55% ethanol（containing 0.1 mol/L citrate-phosphate buffer, pH 5.0, liquid-to-solid ratio of 30∶1 mL/g）, flavonoids were extracted under ultrasonic conditions of 300 W, for 50 min, and at 50 ℃. A HaCaT cell model damaged by 150 mJ/cm² UVB was established, including a blank group（C）, a model group（UVB）, and Hippophae rhamnoides Linn. flavonoid low/middle/high dose groups（HRF-L/M/H, 100, 200, 400 μg/mL, respectively）. After treatment with Hippophae rhamnoides Linn. flavonoids, cell viability and proliferation were detected by MTT and EdU assays, and the activities of catalase（CAT）, superoxide dismutase（SOD）, and glutathione peroxidase（GPX）, as well as the levels of reactive oxygen species（ROS）and malondialdehyde（MDA）were analyzed using commercial kits. The extraction yield of flavonoids after process optimization in this study is（9.92±0.44）mg/g, which is higher than those reported in previous literatures. Compared with the C group, the cell viability and EdU positive rate in the UVB group decrease, the activities of CAT, SOD, and GPX decrease, and the levels of ROS and MDA increase（P<0.05）. Compared with the UVB group, the cell viability and EdU positive rate in the HRF-L/M/H groups increase, the activities of CAT, SOD, and GPX increase, and the levels of ROS and MDA decrease（P<0.05）. This study demonstrates that the composite enzymatic hydrolysis-ultrasound synergistic method can achieve efficient extraction of flavonoids from Hippophae rhamnoides Linn. pomace. Hippophae rhamnoides Linn. flavonoids alleviate UVB-induced damage to HaCaT cells by enhancing the activities of antioxidant enzymes, scavenging ROS, and inhibiting lipid peroxidation. This study provides theoretical support for the resource utilization of Hippophae rhamnoides Linn. pomace and the development of natural antioxidants.

Key words: Hippophae rhamnoides Linn., flavonoids, antioxidant, HaCaT cells, cosmetics