Saponins extracted by ultrasound from Zizyphus jujuba Mil var. spinosa leaves exert resistance to oxidative damage in Caenorhabditis elegans

This work aims to investigate antioxidant activities of saponins extracts from Zizyphus jujuba Mill var. spinosa leaves (ZSL). In this study, saponins were extracted by ultrasound-assisted method, Box-Behnken design (BBD) and response surface methodology (RSM) were applied to obtain the optimal extraction conditions were as follows: ratio of liquid to material 36:1 mL/g, ethanol concentration 50%, ultrasonic power 381 W, extracting time 50 min, and the highest extraction rate was 15.54 ± 0.19%. Then the antioxidant activity of ZSL saponins was evaluated by antioxidant activity assay in vitro and in Caenorhabditis elegans ( C. elegans ). The half maximal inhibitory concentration (IC 50 ) of ZSL saponins on DPPH radicals, ABTS radicals and hydroxyl radicals were 1.19 mg/mL, 0.35 mg/mL and 0.38 mg/mL, respectively, and exhibited strong reducing power, showing good antioxidant activity in vitro. In addition, ZSL saponins had an effective role in the resistance to oxidative damage in C. elegans : enhancing the resistance to heat stress and hydrogen peroxide (H 2 O 2 ) oxidative stress, ameliorating the chemotactic ability, inhibiting the accumulation of reactive oxygen species (ROS), increasing the activity of glutathione s-transferase 4 (GST-4), superoxide dismutase 3 (SOD-3), glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD), and decreasing the content of malondialdehyde (MDA).