Modulation of the interaction of Coumarin 7 with DNA by β-cyclodextrin

The possible structure of the host-guest complex, Coumarin 7/beta-cyclodextrin and the site of binding with DNA are optimized by UV-Visible absorption, fluorescence, molecular modeling and Nuclear Magnetic Resonance spectroscopy techniques. The study of the effect of acid strength on the absorption and emission of Coumarin 7 in the presence and the absence of beta-cyclodextrin shows that Coumarin 7 becomes less basic in the excited state and the encapsulation by the host molecule makes it less susceptible to get protonated. Coumarin 7 is encapsulated by beta-cyclodextrin, forming a 1: 1 inclusion complex. It binds to DNA with a binding constant of 3.45 x 10(5) M-1. The role of beta-cyclodextrin on the binding of Coumarin 7 with calf thymus DNA is explained. The possibility of beta-cyclodextrin encapsulation to the exposed parts of Coumarin 7-calf thymus DNA complex is reported. These studies provide insight to increase the aqueous solubility and bioavailability of Coumarin 7 by the formation of an inclusion complex with beta-cyclodextrin.