The Application And The Research Of Optical,Antioxidant Activity Properties About Two Anthocyanins At Different PH

Chapter 1:This chapter first summarizes the types of anthocyanin,chemical structure,biological activity and the pH effect on it.Secondly,the principle and the significance of density functional theory were briefly introduced.Furthermore,the damage of free radicals,and the function of antioxidants,as well as the development and application of natural edible pigment as antioxidants were presented.Finally,the research background,main contents and innovative points were presented.Chapter 2:This chapter examines the UV-Vis and fluoscence spectral changes of two anthocyanins（cyanidin chloride and delphinidin chloride）at different pH aqueous solution.The results reveal there are different transitions for each anthocyanin at different pH with different emission spectrum,suggesting the different electronic transitions at different pH.The absorption spectrum of cyanidin chloride varies greatly with the change of pH.There may exist four stable structures at each different pH solution:quinonoidal anhydrobase（A:A₁,A₂,A₃ resonators）,flavylium cation（AH⁺）,carbinol pseudobase（B）,chalcone（C）,with the maximum emission at 649nm,628 nm,382 nm,430 nm respectively.The spectrum of delphinidin chloride varies slightly,and at various pH it may have three different structures:quinonoidal base（A:A₁,A₂ resonators）,carbinol pseudobase（B）,chalcone（C）.There is only a slight difference on the absorption and emission spectra for the three different structures.The quantum yield of two anthocyanins is very low at different pH aqueous solution.The primaryprocess from the excited state to the ground state is non-radiative decay.The core structure of delphinidin chloride and cyanidin chloride is the same,other than another extra hydroxyl group in delphinidin chloride.However,there absorption and fluoscence spectrum change dramatical for these two anthocyanins.The number and location of the hydroxyl groups have a great impact on the activity,stability and antioxidant activity of anthocyanins compounds.Chapter 3:The structure of cyanidin chloride and delphinidin chloride at different pH aqueous solution were geometrically optimized by using the Density Functional Theory B3LYP method with 6-31G basis set.The data set of molecular structure parameters,frontier molecular orbital energy and the hydroxyl radical’s Mulliken charge distribution indicated that the antioxidation activity of C_4’phenolic hydroxyl group is greater than that at other positions,such as at C₃,C₅ and C₇.In addition,with the change of pH,the antioxidation activity of generated quinoid alkali compounds probablly is higher than other structure forms.Delphinidin chloride may have a better antioxidant activit y than cyanidin chloride.This chapter is the foundation of the further research about the mechanism of anthocyanins as antioxidants in aqueous solution with different pH values,and it also provided some suggestion for the modifaction of anthcyanins to achieve better biological properties.Chapter 4:The purple sweet potatos contain an abundant amount of anthocyanin,which displays different colors at different pH Based on the color changes at varied acidic or basic conditions,we provide a method to make colored purple potato paste and use it to make steaming buns,noodles,baked bread or colorants forcake,etc.From the color change at varied pH conditions,we provided a method for the quick detection of anthocyanin pigment in different products,such as purple potato biscuits,blueberry jam,wine and so on.The method is fast,accurate,easy to operate at less cost and non-toxic environmental impacts.