268 Determination of the Thermodynamics Parameters of the Complexation of Chlorogenic Acid by b-Cyclodextrin

Thursday, November 5, 2009: 11:40 AM
Rio Grande (Camino Real Hotel)
Ricardo Palos Pacheco , Instituto de Ciencias Biomedicas-Departamento de Ciencias Basicas, Universidad Autonoma de Ciudad Juarez, Juarez, Mexico
E. Alvarez-Parrilla , Instituto de Ciencias Biomedicas-Departamento de Ciencias Basicas, Universidad Autonoma de Ciudad Juarez, Juarez, Mexico
L.A. de la Rosa , Instituto de Ciencias Biomedicas-Departamento de Ciencias Basicas, Universidad Autonoma de Ciudad Juarez, Juarez, Mexico
Bernardo A. Frontana-Uribe , Instituto de Química, Universidad Nacional Autonoma de Mexico, Mexico DF, Mexico
The complexation of chlorogenic acid (CGA) by b-cyclodextrin (bCD) is an important issue in food technology and the biochemistry of several plants, because the consequences of its formation could provide new insights for the understanding of enzymatic browning on fruits. CGA is an o-diphenolic acid, derived from trans-cinamic and (-)-quinic acids; and it is the most abundant polyphenolic antioxidant of apple and coffee. The bCD is a macrocyclic oligomer of seven blocks of glucopiranose. This macrocyclic array forms a cavity where molecules of specific shape and size, like chlorogenic acid, can be included. This interaction between bCD and CGA forms a supramolecular complex. Weak non-covalent forces and molecular recognition play important roles on the stability of the complex.
The CGA complexation by bCD requires a description of its thermodynamics parameters (ΔGo, ΔHo, ΔSo & K ) in order to obtain an explanation for the data obtained in an earlier work by Alvarez-Parrilla et. al. in 2007. The experimental techniques used were steady-state fluorescence, ITC, cyclic voltametry, and RMN-ROESY.           
It could be determined that CGA complexation by bCD is more complicated than it had proposed. In this study is exposed that CGA molecule can be complexed by both polyphenolic and quinic acid moiety. This leads to the formation of supramolecular isomers with 1:1 stoichiometry. By steady-state fluorescence was determined the microscopic stability constant of the polyphenolic moiety complexation; and by ITC, the macroscopic stability constant of the supramolecular process. The RMN-ROESY and cyclic voltametry experiments showed the molecular details about the complexation.