Antioxidant Activity Of Raspberry Extract And Its Protective Effects And Mechanism On Oxidative Damage Of HepG2 Cells

Modern studies have shown that oxidative stress caused by imbalance of redox levels in the body is the pathophysiological basis of many diseases.Some antioxidant ingredients in natural products can scavenge free radicals,restore the home’s redox levels to a dynamic balance,thereby reducing oxidative stress damage of the body.Raspberry,as the third generation of golden fruit which is recommended by the World Food and Agriculture Organization（FAO）,has been shown to have strong antioxidant activity.Therefore,we aimed to investigate the protective effect of raspberry extract and its major anthocyanins on oxidative stress in HepG2 cells.（1）Raspberry was extracted followed by flash extractor,and the extraction process parameters were optimized by single factor test and response surface analysis.The experimental results showed that the optimal extraction process parameters of raspberry extracts were: ethanol volume fraction 48%,voltage 150 V,extraction time 57 s,and the extraction amount of raspberry polyphenols was（52.244 ± 0.662）mg/g dried fruit.（2）The major components were identified fourier transform infrared spectroscopy and high performance liquid chromatography.The experimental results showed that TPC,TFC and TAC in raspberry extract were 10.286 ± 0.396 mg equivalent gallic acid,15.833 ± 2.890 mg equivalent rutin and 2.467 ± 0.035 mg equivalent cyanidin-3-glucoside,combined with Fourier transform infrared spectroscopy and High Performance Liquid Chromatography（HPLC）analysis,RE main ingredients are phenolic acids,flavonoids and flavonoid glycosides of polyphenol compounds,and its main component is cyanidin-3-glucoside,content amounted to 33.59% of RE.（3）The antioxidant activity of raspberry extract and its majorcomponent was determined by in vitro test.The results of the experiment showed that raspberry extract and cyanidin-3-glucoside have showed good antioxidant activity in vitro,and in the case of DPPH free radical scavenging ability,raspberry extract showed stronger than the cyanidin-3-glucoside in the total antioxidant capacity,this could be due to a variety of material within the RE exists between synergy,which enhance the antioxidant effect.（4）Hydrogen peroxide（H₂O₂）was consequently used to induce HepG2 cells to establish an oxidative stress model,which was conducted to evaluate the protective effect of raspberry and its major anthocyanins on oxidative stress.The results showed that 4 M H₂O₂ could be used to construct the oxidative damage model of HepG2 cells.When HepG2 cells were subjected to oxidative damage by H₂O₂,the cell viability（survival rate）,GSH content and CAT activity were significantly changed,and the activity of HepG2 cells could be significantly enhanced by raspberry extract and Cyanidin-3-glucoside.The level of ROS in injured cells was decreased and the level of CAT activity and GSH in cells was increased.Western Blotting results showed that raspberry extract and cyanidin-3-Glucosides were involved in the Keap1/Nrf2 signaling pathway,regulating the expression of the downstream target proteins HO-1,NQO1 and γ-GCS of the signaling pathway,thus protecting HepG2 cells from oxidative stress.Conclusion: raspberry extract and its major anthocyanin,Cyanidin-3-glucoside,have strong antioxidant activity and can participate in the Keap1/Nrf2 signaling pathway to protect HepG2 cells from oxidative stress.