Free Radical Scavenging Ability Of The Lotus Shell And Its Protective Effect Against Oxidative Damage In Cells

Free radical formation is considered as normal human metabolite process. However, the exposure to ultraviolet radiation, chemical pollution and other external stimuli may create an imbalance antioxidant system, leading to the damage of nucleic acids, mitochondria and other organelles, resulting in various symptoms and diseases. Lotus shell can be described as the mature, dried receptacle of genus Nymphaeaceae perennial herb(Nelumbo nucifera Gaertn.) which is used mainly in hemostasis, antisepsis, and other aspects of myocardial protection. Lotus shell was selected as its experimental material, this study was intended to explore free radical scavenging ability of lotus shell and protective effect against oxidative damage in cells. The experiment proceeded in four stages: optimization of lotus shell flavonoid extraction conditions; screening of the active compound lotus shell; identifying the structure of active compound in lotus shell and protective effect against hydrogen peroxide induced damage in cells. Results of the study are as follows:(1) The yield of total flavonoid from lotus shell was used as the indicator and then explored the effects of ultrasonic extraction time, extraction temperature, liquid ratio and ethanol volume fraction towards lotus shell total flavonoid extraction rate. By response surface analysis the optimum conditions were: liquid ratio 40 mL/g, 48% ethanol concentration, extraction temperature 60 °C, and extraction time 10 min.(2) The free radical scavenging activities were used as the indicator and then explored the antioxidant capacity of different polarity parts of lotus shell. Results showed that different polarity lotus shell parts showed antioxidant capacity in dose-dependent manner, of which medium polar ethyl acetate showed the strongest activity.(3) By using new detection methods as HPLC、ESI-MS、NMR, structure of active compound from ethyl acetate fraction of lotus receptacls was identified. Comparison with scientific literature correlations determined the substance as quercetin-3-O-β-D- glucoside(QOG).(4) Docking study showed that monomer compound QOG had a protective effect against H2O2-induced damage in CCD-986 sk cells accroding to inhibite NF-?B activation.