Synthesis And Antioxidant Activity Of Baicalein And Scutellarein

Baicalein and Scutellarein are the main active ingredients of Scutcllaria Baicalensis Georsi and Erigeron breviscapus, which have various pharmacological effects, such as antiviral, antioxidant, anti-tumor, anti-aggregatory, anticancer, dilation of blood vessels, platelet count and protect the liver, neurons, heart and brain blood vessels. Baicalein and Scutellarein tablets or injections have become commonly used in clinical medicine, its main source come from natural or cultivated Scutcllaria Baicalensis Georsi and Erigeron breviscapus. But they have low yield to extract from plants and costs much. Therefore, it has significant meaning to prepare Baicalein and Scutellarein by designing rational chemical route. As prepare Baicalein and Scutellarein by rational chemical route can avoid occupation of arable land, reduce costs, environmentally friendly and help improve the quality of medicines, the study on them shows importance significance.In this experiment we try to prepare Baicalein and Scutellarein through chalcone method. We start from 3,4,5-trimethoxybenzoic acid then nitrification and decarboxylation, reduction with the iron powder and finally diazo to get 3,4,5-trimethoxyphenol. We also get cinnamic chloride, p-methoxy cinnamic acid chloride from benzaldehyde, p-methoxy benzaldehyde. With the help of BF3-Et2O complex, 3,4,5-trimethoxyphenol was directly acylated with cinnamoyl chlorides to give corresponding chalcones by Fries rearrangement. Under the action of I2/DMSO, 5,6,7-trimethoxylflavone and 5,6,7,4′-tetramethoxylflavone were feasible obtained by intramolecular cyclization of chalcones. Finally, the demethylation of 5,6,7-trimethoxylflavone and 5,6,7,4′-tetramethoxylflavone were performed to give the desired Baicalein and Scutellarein. In the process of synthesis of chalcones, we investigated the effect of temperature. The result showed the suitable reaction temperature was 70℃. We also derived that the yield of 5,6,7,4′-tetramethoxylflavone was best as the mole ratio of 9-Hydroxy-5,6,7,4′-tetramethoxychalcone and Iodine was 10 :1. It was the first time to use hydrobromic acid hydrolysis of 5,6,7,4′-tetramethoxyflavone to Scutellarein. By Infrared Spectrum, Liquid Chromatography–Mass Spectrometry and Nuclear Magnetic Resonance Spectrumwe determine the structure of every product we get.Baicalein and Scutellarein are molecules with multiple hydroxyl groups, which have strong antioxidant activity. Compare with common antioxidant butylated hydroxytoluene(BHT), we get strength of the three antioxidant capacity as follows by spectrophotometry: the capacity of remove superoxide anion radical O2-·: Scutellarein is the strongest, Baicalein is the second and BHT is the weakest; the capacity of remove hydroxyl free radical·OH: Scutellarein is the strongest, Baicalein is the second and BHT is the weakest. Antioxidant activity of Scutellarein has not been reported.