Complexation Reactions Of Myricetin With β-cyclodextrin And Its Derivatives

Myricetin (Myr) belongs to a large group of naturally flavonol compounds. It has many physiological activities, and its source is broad. Now the research focusing on Myr is about pharmacological aspect. It also can be used as natural antioxidant and food preservative in food industry or be developed health food. However, since such applications are often limited by its poor water solubility, instability to light and alkali, bitter taste and other limitation, then it is very necessary to search a good method to mend these unfavorable physicochemical properties.The researches about Myr in this thesis included four aspects:(1) The researches about the complexation reaction of Myr with p-cyclodextrin (β-CD) and its derivatives (mono[2-O-(2-hydroxypropyl)]-β-CD (HP-β-CD), mono[2-O-(2-hydroxyethy 1)]-β-CD (HE-β-CD), and heptakis (2,6-di-methyl) -β-CD (DM-β-CD)) using fluorospectrometry spectra. Result shows that the complexation between Myr and cyclodextrins (CDs) could cause the fluorescence enhancement, and the maximum excitation wavelength slightly shifted to shorter wavelength. The stoichiometry ratio was found to be 1:1, and fluorescence enhancement of CDs followed the order: HP-β-CD>HE-β-CD> DM-β-CD>β-CD. The effect of temperature on the formation of HP-β-CD- Myr inclusion complex was also been examined.The thermodynamic measurements suggest that the inclusive process was an exothermic reaction and enthalpic favour.(2)Formation was also evaluated by comparing the infrared spectra of the solid complexes with a simple physical mixture containing the same amount of Myr. Experiments provided data indicating the formation of HP-β-CD-Myr complexes. The content of Myr in the microcapsules was 43.8 mg/g HP-β-CD-Myr.(3)Antioxidant activity of Myr was enhanced by formation with HP-β-CD in acidic potassium chlorate solution. The measurements of reductive ability was investigated from the Fe³⁺ - Fe²⁺ transformation, Result shows that complexation with HP-β-CD improved the reductive capability of Myr. The antioxidant activity of Myr and HP-β-CD- Myr in linoleic acid system was also investigated. The complexes showed a higher antioxidant activity then Myr. Lower hydroxyl free radical scavenging efficacy of HP-β-CD-Myr might be contributive to some hydroxy groups of Myr inserts into the cavity of CDs.(4)Research found that the HP-β-CD- Myr was more stable to light than Myr. During short storage time in methanol solution, the metal ion namely K⁺,Na⁺,Mg²⁺,NH₄⁺,and Ca²⁺ had not notable effect on Myr stability.But the metal ion namely AL³⁺,Fe³⁺,and Cu²⁺ destroying destroy its stability should be avoided.