Pharmacological Comparison Of Flavonoid Glycosides And Aglycones On Their Anti-oxidation And Anti-fatigue Activities

Free radicals, produced during the course of organism supersession, have strong oxidation capacity. When free radicals are produced excessively or eliminated ineffectively, intracellular redox homeostasis will be disrupted. The subsequences comprise protein denaturation, DNA degradation and lipid peroxidation, which will lead to a variety of diseases. Therefore, studies on free radicals scavengers or antioxidants have become the hot topic in the current medical and pharmaceutical researches.Flavonoids compounds are distributed widely in the nature with diverse structures and significant anti-oxidative activities in vivo and in vitro. In recent years, lots of flavonoid compounds have been found to display excellent antioxidant activity, and their antioxidative mechanism has been exploited intensively. However, the comprehensive evaluation of these compounds is lacking of systematic study on their antioxidant capacity, pharmaceutical preparation, pharmacodynamics effects and pharmacokinetics.In this thesis, based on the structure activity relationship of flavonoids antioxidant capacity, eight kinds of flavonoids (four flavonoid glycosides and their aglycone) were selected for comparative studies of antioxidant activity in vitro. Then, baicalein was chosen for pharmaceutical preparation, pharmacodynamics effects and pharmaco-kinetics studies systematically. The results will afford experimental basis for developing potential antioxidative drug in clinical. The specific works are as follows:1.The method of UV-Vis spectrometry was used to study the scavenging activity of eight kinds of flavonoids compounds for ONOO-, ?OH and O2·- in vitro. The results showed that these compounds were all effective for inhibiting nitration reaction of protein aroused by ONOO-, and scavenging ?OH and O2·-. Among these compounds, baicalein showed the most significant effect. 2.In order to improve the drug stability stabilities and pharmacodynamic effects of flavonoids compounds, sustained-releasing baicalein liposomes were formulated successfully. Comparison of three conventional methods for preparing liposomes showed that the liposomes were formulated by ether injection method has higher and more stable drug encapsulation efficiency. Through orthogonal experiments, it was found that the optimum conditions for preparing baicalein liposomes were as follows: lecithin : cholesterol = 8:1, 0.020 g of baicalein should be dissolved in 20 mL of PBS (pH 6.7), and 0.060 g of cholesterol in 15 mL of ether. In this conditions, the average encapsulation efficiency of baicalein liposomes was 41.5±4.77 %, size distribution with 400-600nm. At the sustained-release time of 24 h, the drug cumulative release ratio was up to 91.2%.3.Drug safety of baicalein was evaluated by acute toxicity test and medium-term toxicity test. After the drug was given intragastrically once, the results showed that the LD50 of baicalein at 24~48 h was 3000 mg/kg and > 2000 mg/kg at 14 d. The medium-term toxicity test indicated that baicalein could exert toxic effect on liver, spleen and kidney in mice, and kidney injury was the most significant.4.By given intragastrically to mice for 14 d continuously, the anti-fatigue activity of baicalein itself and baicalein liposomes was explored. The results showed that, compared with the movement control groups, serum LD and MDA content in drug groups were reduced and SOD activities were enhanced, the time of swimming to exhaustion was prolonged. Among four drug groups, low-dose baicalein liposomes group presented the significant differences, which indicated that baicalein liposomes had outstanding anti-fatigue activity. In addition, the tests of biochemical indexes showed that baicalein could reduce the blood glucose and lipid, especially the blood lipid.5.Determination of baicalein concentration in plasma by HPLC was established. The results indicated that this method was reliable for high specificity, simple operation, complete separation and reliable results. This mothod was also suitable for the bioequivalence research, and the pharmacokinetic study of baicalein liposomes for the relative recovery rate was between 85~115% and the coefficient of inter-day and intra-day variation was less than 10%. Therefore, the pharmacokinetics of baicalein liposomes in mice was studied by HPLC. The drug-time curve showed that baicalein liposomes had appropriate release rate. After treated for 3 h, the blood drug concentration achieved the peak value. At the time intervals of 3~6 h, drug's absorption and elimination rate were roughly equal, and the drug was at the stationary phase. After 6 h, the blood drug concentration declined gradually. Still there were a small amounts of baicalein released after 24 h. In conclusion, baicalein liposomes prepared in this thesis were provided with enhanced effect and sustained-release feature, and could become new drugs in clinical.