Study On The Antioxidant Activity Of Extracts From Chinese Wolfberry And Its Protective Effect On HepG2 Cells' Oxidative Damage

Lycium ruthenicum Murr is a unique kind of wild plant with tolerance of high salinity and drought in the northwest of our country. The fruit of Lycium ruthenicum Murr could be applied as Chinese medicine in the traditional Chinese medicine preparation. It could also be applied daily edible ways such as making tea and being steeped in wine. It is a kind of pharmaceutical/food resource. It has been reported by literature in recent years that Lycium ruthenicum Murr has many biological activities, such as anti-fatigue, anti-diabetes and anti-hyperlipidemia. However, there is not much research of the antioxidant activity in vitro of Lycium ruthenicum Murr and its extractives. Lycium ruthenicum Murr of Qinghai is used as the material in this research and its nutrition and active ingredients are tested. The extraction condition, stability, the main composition of polyphenols, and its protection of human HepG2 from oxidative damage are investigated. Plant chemical composition and the oxidation resistance of the brewed liquid of Lycium ruthenicum Murr are tested. The results of the research are as follows:1. The main nutrients and active ingredients of Lycium ruthenicum Murr are tested. The results show that the protein and crude fat contents of Lycium ruthenicum Murr are 10.35% and 5.89% respectively. The moisture content of dried fruit is 10.61%. The contents of Fe, Zn and Mn are 58.50、2.05 and 1.961 mg/100 g respectively. The heavy metal content is low and the level of pollution is low. The anthocyanin content is 939.27 mg/100 g. The contents of total phenol and total flavonoids are 45.05 and 56.54 mg/g respectively. The total sugar content is 7.83% and the content of ascorbic acid is 9.90 mg/100 g. It means that the wild Lycium ruthenicum Murr of Qaidam has high nutritional value.2. The extraction condition of Lycium ruthenicum Murr is determined through single factor experiment:Ethanol solution with a volume percentage of 50% is used as the extraction solvent with extraction time of 2 h. The extractives are not stable under heat or illumination and the antioxidant activity decreases with the increase of heating temperature and illumination intensity. The decomposition of anthocyanin of Lycium ruthenicum Murr satisfies the first-order kinetic. Under the heating conditions of 80 and 100℃, the half-time of anthocyanin are 5.87 h and 2.50 h respectively. Illumination decreases the content of anthocyanin in extractives. The longer it is placed, the more antioxidant capacity is reduced. The decreasing order is indoor natural light>outdoor natural light> away from light and indoor. The half-time of anthocyanin is 69.59 days under the condition without light.3. The antioxidant activity of Lycium ruthenicum Murr extract is evaluated and is compared with those of red Chinese wolfberry and Vc. The abilities of Lycium ruthenicum Murr extrac to eliminate hydroxyl radicals and total antioxidant capacity are higher than Vc and red Chinese wolfberry extract of same concentration. The ability to eliminate DPPH free radicals is lower than Vc. The analysis result of polyphenols ingredients in extract using HPLC-MS shows that extractives contain cyanidin-3-O-glucoside chloride and 1-Benzopyrylium etc.4. Lycium ruthenicum Murr extract have protective effects for the oxidative damage of HepG2 cells. Its main performance is that Lycium ruthenicum Murr extractive with a concentration of 0-1000 g/mL has no significant influence for the livability of HepG2 cells. The condition to build damage model of HepG2 cells is 500 μM H2O2 with a processing time of 2 h. The livability of detection model using MTT method is 58.17%. The livability could be increased to 70.49%,73.35% and 75.54% respectively using nutrient solutions of Lycium ruthenicum Murr extract with concentrations of 250,500 and 1000μg/mL for pre-protection for 24h. The SOD enzyme level could also be increased. The LDH and MDA levels of cell culture fluid could be decreased significantly (P<0.05). At the same time, testing results of flow cytometry show that extractives could increase the G0/G1 periods of oxidized and damaged cells. The early apoptosis rate decreases from 25.52% to the range of 8.92-14.13%.5. The dried fruit of Lycium ruthenicum Murr has best performance when steeped using 100 ℃ water for 90 min. Under this condition, the contents of anthocyanin, total polyphenol, total flavonoids and total sugar of the brewed liquid are 3.23、102、17.98 and 33.95 mg/100mL respectively. The ability to eliminate DPPH free radicals is 48.93% and the FRAP value is 3.93 mmol/L. With the increase of brewing time, all the indicators reduce.