Molecular encapsulation of Valganciclovir by β-cyclodextrin influences its binding to bovine serum albumin: a spectroscopic study

We report, in this paper, the stoichiometry, the binding constant and the structure of the beta-cyclodextrin complex of the famous drug Valganciclovir. We investigate the influence of the complex formation of Valganciclovir with beta-cyclodextrin, in the binding strength of the drug to the model carrier protein bovine serum albumin. Based on the electronic absorption, fluorescence and 2D rotating-frame Overhauser effect spectroscopy (ROESY) NMR spectral data, it follows that Valganciclovir forms a 1:1 complex with beta-cyclodextrin. The beta-CD molecule encapsulates the aliphatic chain of the substituted ester molecule. The association constant value of the drug-protein binding in the presence of beta-cyclodextrin decreases from that in the absence of beta-cyclodextrin, i.e., from that in the case of free drug, i.e. from 3.99 x 10(4) M-1 to 5.21 x 10(3) M-1. We compare the results of the binding of the drug to bovine serum albumin in free- and beta-cyclodextrin-complex forms.