Extraction, Purification And Antioxidant Acitivity Analysis Of Hydroxytyrosol From Oil Olive Leaves

There are many kinds of antioxidant active substances in olive leaves such as flavonoids, lignan, oleuroprin. Oleuroprin can be transformed into hydroxytyrosol, which has some healthy function such as antiseptic, anti-inflammation and prevention atherosclerosis. It has potential significance to utilize oil olive leaves resources.This paper researched the method of transforming oleuropein into hydroxytyrosol, the optimum extraction and purification conditions, and its antioxidant activities and lowering blood lipids level of mice with hyperlipemia. The extract of olive leaves was hydrolyzed by hydrochloric acid and β-glycosidase respectively to prepare hydroxytyrosol. The orthogonal design was adopted to find out the optimal processing conditions of both methods. The results showed that the optimal hydrochloric hydrolysis conditions as following:hydrochloric acid concentration0.2mol/L, ration of solvent volume to extract of olive leaves (mL/mg)50:1, and hydrolyzing for6h at80℃; the optimal enzymatic hydrolysis conditions are as follows:pH7.0. enzyme concentration25U/mg, and hydrolyzing for4h at50℃. In view of production cost and the yield of hydroxytyrosol, the method of hydrochloric acid is better than that of enzymatic hydrolysis.On the basis of single-factor test, the response surface methodology with4factors and3levels was adopted. Based on the single factor analysis, Box-Behnken experimental design was taken to evaluate the effects of the four factors. These results showed that the optimal extracting conditions were:hydrochloric acid concentration was0.14mol/L, extraction time was6h. extracting temperature was92.39℃. and the ratio of solvent to solid was50.74:1(mL/g). the maximum yield of hydroxytyrosol was0.580%. The validation test showed that the prediction values of the model were well agreed with the experimental values.Compared with several type adsorption resins, DM-2was the best. After the purification, yellow creamy was obtained, and the content of HT was about66%, DM-2resin enrichment fold was6.5.With different concentrations, the reducing power, the scavenging power of OH· and DPPH· of HT, Res, olive leaves extraction, Vc were compared. The results showed that HT had strong antioxidant in vitro which was even stronger than Vc. Through animal experiment, HT could decrease blood lipid level of mice with hyperlipemia obviously. The content of TC and TG in serum of mice, which ate suitable HT, dropped obviously, while the content of HDL-C rose. HT also increased T-AOC levels, SOD activity, and reduced MDA content in liver.