Study On Antioxidative Substance Of Chinese Bayberry Bark, Leaves And Fruits

Chinese Bayberry, Myrica rubra (Lour.) Sieb. et Zucc (Family Myricaceae),is a perennial evergreen tree. It is noteworthy that different parts of this plant are used in traditional herbal medicine or folk recipes because of their various pharmacological activities such as the antioxidant, neuroprotective and anticancer activities. In present study, we focused on investigation in vitro antioxidant substance of the bark, leaves and fruits of Myrica rubra.Firstly, the in vitro antioxidant activities were evaluated by means of the chemical method and the cytobiological method. The chemical methods, including radical scavenging activity (DPPH·) and ferric reducing antioxidant power (FRAP), were adopted, and the results of antioxidant abilities of the bark, the fruits, the leaves of the Chinese Bayberry exhibited:the bark> the fruits> the leaves.H2O2-induced PC 12 cells oxidative stress damage model were used as the cytobiological method to evaluate their antioxidant abilities. The MTT assay results showed that the bark extracts at the dose between 25 and 50μg/ml as well as the fruits extracts at the dose beyond 50 μg/ml displayed good neuroprotective activities, but the leaves extract didn’t exhibit such property. Flow cytometry also proved that the extracts from the bark and the fruits of Myrica rubra could partially reverse hydrogen peroxide induced apoptosis in PC 12 cells, however, the leaves extract didn’t display any effects. The biochemical analysis revealed that the bark and fruit extracts exhibited the antioxidant activity through reducing intracellular ROS and MDA contents, as well as increasing the activity of SOD. Based on above, we draw the conclusion that the methanolic extract from the bark of Myrica rubra has stronger antioxidant activity among the three parts.In order to study the antioxidant constituents of the bark of Myrica rubra, various chromatographic techniques, including silica gel, Sephadex LH-20 and preparative HPLC were used to isolate the single compounds from the methanolic extract of the bark. Fourteen compounds were isolated, and their structures were identified on the basis of chemical properties and spectroscopic data, as 3,5-dimethoxy-4-hydroxy myricanol, Myricanol, Myricanone, Myricanol 11-sulfate, Myricitrin, Quercetin, Quercetin-3-rhamnoside, Tamarixol, Uvaol, Ursolic Acid, Taraxerol, Myricadiol, β-sitosterol, β-daucosterol. Among them, a new compounds named as 3,5-dimethoxy-4-hydroxy myricanol, Tamarixol and Uvaol were isolated from the genus, Myrica, for the first time.Six major compounds (three flavones:Myricitrin, Quercetin, Quercetin-3-rhamnoside and three diarylheptanoids:Myricanol, Myricanone, Myricanol 11-sulfate) were screened by two oxidative stress damage models, glutamate or hydrogen peroxide induced PC 12 cells damage models, respectively. The results indicated that all the three flavones have good cytoprotection in both in vitro screening models, and Myricitrin possesses the best activity. Only Myricanol 11-Sulfate showed cytoprotection among the three diarylheptanoids, which has the substitute group with the C11-SO3H. Flow cytometry also proved Myricitrin and Myricanol 11-sulfate can partially reverse the cell apoptosis induced by glutamate. The biochemical determination revealed that Myricitrin and Myricanol 11-sulfate have the cytoprotective effects through reducing intracellular ROS and MDA contents, as well as increasing the SOD activity.From what has been discussed above, the antioxidation of the bark, the leaves and fruits from Myrica rubra. was significant positive correlation with their contents of total flavones and total polyphenols. Therefore, polyphenols and flavones are likely the primary substance for antioxidantion.In addition, the chemical constituents and pharmacological activities of Myrica are also reviewed, which provided the reference for the design in this thesis.