The kinetics of formation of resveratrol-beta-cyclodextrin-NH2 and resveratrol analog-beta-cyclodextrin-NH2 supramolecular complexes

The determination of the kinetics of inclusion processes is significant for the application of inclusion complexes as carriers for bioactive molecules. We determined the kinetic parameters of inclusion between modified beta-cyclodextrin (beta-CD-NH2) and the polyphenols resveratrol (RES) and its structural analog (RESAn1), using the real-time analysis of surface plasmon resonance. The association and dissociation rate constants (k(a) and k(d)) showed that RESAn1 inclusion and its dissociation from beta-CD-NH2 were faster than a similar process for RES (k(a)(beta-CD-NH2/RESAn1) = 3.10.10(4) +/- 0.14 M(-1)s(-1), k(a)(beta-CD-NH2/RES) = 1087.103 +/- 0.11 M(-1)s(-1); k(d)(beta-CD-NH2/RESAn1) = 0.39 +/- 0.02 s(-1), k(d)(beta-CD-NH2/RES) = 0.30 +/- 0.02 s(-1), at 25 degrees C). The activated complex formation was also affected by the structural differences between the polyphenols, as showed by the activation energies of the association step (E-act, a(beta-CD-NH2/RES) = 14.81 +/- 0.64 kJ.mol(-1), E-act, a(beta-CD-NH2/RESAn1) = -15.01 +/- 0.75 to 82.35 +/- 4.47 kJ.mol(-1)). These effects of polyphenol structural differences are due to the desolvation process of interacting molecules. These results elucidate the role of small group to the dynamics of the molecular inclusion of beta-CD.