Preparation Of Saponins From Sour Jujube Leaves And Its Antioxidative Damage Effect

During the metabolism of organisms,various active oxygen free radicals are continuously produced.Appropriate amount of oxygen free radicals plays an important role in maintaining the health of the body,however,when oxygen radicals are generated too much,it will cause oxidative damage to the body,causing various diseases such as cancer,atherosclerosis,and senile dementia.Zizyphus jujuba Mill var.spinosa leaves（ZSL）,is the leaves of the Ziziphus jujuba Mill var.spinosa（Bunge）Hu ex H.F.Chow,with a calming nerve,sedative and hypnotic effects.Phytochemical studies have indicated that ZSL contains various natural compounds,including saponins,phenolic acids,flavonoids,and so on.Among them,the saponins are its main components.However,there have been few studies so far on exploring ZSL saponins despite its great potential in health care.Therefore,the response surface method was used to optimize the ultrasonic-assisted extraction process of saponins from ZSL,and a variety of antioxidant activity research methods in vitro were used to explore its antioxidant activity.On this basis,the protective effect of ZSL saponins on oxidative damage was studied by using Caenorhabditis elegans（C.elegans）as a model.The research results are as follows:（1）Using the response surface method to optimize the ultrasonic-assisted extraction process of saponins,and to investigate the factors affecting the extraction rate of saponins from ZSL.On the basis of single factor experiment,the liquid to material ratio,ethanol concentration,ultrasonic power and ultrasonic time were used as independent variables,and the extraction rate of saponins was used as the response value.Four-factor three-level response surface test was designed to optimize the extraction process by Box-Behnken experiment.The results showed that the effects of various factors on the extraction rate of saponins were as follows:liquid to material ratio>ultrasonic power>ethanol concentration>ultrasonic time.The optimal extraction process conditions were as follows:liquid to material ratio 36:1 mL/g,ethanol concentration 50%,ultrasonic power 381W,and ultrasonic time 50min.The actual extraction rate of ZSL saponins was 15.54±0.19%,which was not significantly different from the predicted value of 15.41%.The response surface model was well fitted with the actual situation and could predict the extraction rate of saponins.（2）The antioxidant activity of saponins from ZSL was studied by using a variety of antioxidant activity methods in vitro.In the range of sample concentrations examined,the reducing power of saponins increased with the increase of sample concentration,and showed a good dose-effect relationship.The reducing power of 0.92mg/mL of saponins was equivalent to that of 60.00μg/mL V_C,and the total reducing power of saponins was about0.0652 times that of V_C.The saponins had a scavenging effect on DPPH radicals,ABTS radicals and hydroxyl radicals,and they also had a dose-dependent relationship,showing a good linear relationship.So it could be calculated that the half maximal inhibitory concentration(IC₅₀)of the saponins on DPPH radicals,ABTS radicals and hydroxyl radicals were 1.19mg/mL,0.35mg/mL and 0.38mg/mL,the scavenging ability were 0.0165,0.0488,0.1406 times of V_C,respectively.（3）Using the model of C.elegans,the effects of saponins on the oxidative damage were investigated by using acute oxidative stress test,chemotaxis assay,fluorescence microscopy and enzyme activity assay.The results showed that compared with the control group,saponins could effectively enhance the resistance of C.elegans to heat stress and H₂O₂ induced oxidative stress,enhanced the chemical sensing ability of nematodes on NaCl and butanone,inhibited the accumulation of reactive oxygen species（ROS）in worms caused by oxidative damage,inhibited the decrease the activity of glutathione s-transferase4（GST-4）,superoxide dismutase 3（SOD-3）,glutathione peroxidase（GSH-Px）and superoxide dismutase（SOD）,and inhibited the increase the content of malondialdehyde（MDA）.It exhibited good anti-oxidative damage and has broad development prospects.