The Chemical Modification Of Quercetin In Hippophae Rhamnoides Flavone And The Study On Quercetin’s Biological Activity

The method of chemical modification of quercetin is studied here. Without interfering active hydroxyl, quercetin sulfonic acid sodium salt is synthesized by reaction of quercetin B ring sulphonyl reaction.The product is characterized by melting point test,IR and 1HNMR.The result shows that the 5th H atom of quercetin B ring is replaced by sulfo group, the objective product is quercetin-5-sulfinic acid sodium.The optimum condition is identified by orthogonal combination of monofactor and multiple factor:the ratio of materials and supplies is 1:6,the reaction time is 3h, the reaction temperature is 90℃,with the yield ratio of 81.85%.The water solubility of quercetin and quercetin-5’-sulfinic acid sodium is compared by contrast test.The mass concentration of them is carried out by linear regression.The result is as follows:the regression equation of quercetin is A=0.0084c+0.4948(R2=0.9983),the solubility is 6.6μg·mL-1 which is obtained on the working curve,the regression equation of quercetin-5’-sulfinic acid sodium is A=0.2110c+0.5675(R2=0.9885),and the solubility is 864.6 μg·mL-1.It is evident that the solubility of quercetin-5/-sulfinic acid sodium is as 130 times as that of quercetin.The reducing activity,clear-away of the superoxide anion, hydroxy radical and ABTS radical of quercetin and quercetin-5/-sulfinic acid sodium are studied by contrast tests.The result shows that the reducing activity of quercetin-5’/sulfinic acid sodium is stronger than that of quercetin;as to the ability of clearing away superoxide anion,EC50 of quercetin-5’-sulfinic acid sodium is 0.2mg·L-1, EC50 of quercetin is 0.4mg·L-1, while EC50 of VC is 0.6 mg·L-1;as to the power of clearing away ABTS radical,TEAC of quercetin-5’-sulfinic acid sodium is 6.52,TEAC of quercetin is 6.04.The bacteriostatic test of quercetin and quercetin-5-sulfinic acid sodium is carried out by filter paper. The result shows that quercetin and quercetin-5’-sulfinic acid sodium both have the power of restraining bacillus proteus,colibacillus and saccharomyces cerevisiae,and the power of restraining bacillus proteus is the best with the MIC of both are125μg·L-1,to colibacillus and saccharomyces cerevisiae,the MIC is 500μg·L-1 and 250μg·L-1 respectively.It is stated clearly that after modification the quercetin has better solubility,higher antioxidant and bacteriostasic activity,all of which expands the application of quercetin.