The influence of β-cyclodextrin encapsulation on the binding of 2'-hydroxyflavanone with calf thymus DNA.

Inclusion complexation of 2'-hydroxyflavanone (2'HF) with β-cyclodextrin (β-CD) was studied, both in solution phase and as solid inclusion complexes, by UV-visible and fluorescence spectroscopic, scanning electron microscopic and X-ray diffractometric techniques. The interaction of 2'HF with calf thymus DNA (ctDNA) in the presence and the absence of β-CD were compared. Fluorescence enhancement was observed for 2'HF due to the formation of 1:1 complex with β-CD. The structure of 1:1 complex is proposed based on spectral observation, molecular modeling and by calculated theoretical bond lengths. The possible mode of interaction between 2'HF and DNA was analyzed by molecular modeling method. The interaction of 2'HF with calf thymus DNA (ctDNA) was investigated by absorption and fluorescence measurements in the presence and the absence of β-CD as capping agent. Both in the presence and the absence of β-CD, 2'HF showed hyper-chromic effect, red shift of absorption spectra, and quenching of fluorescence due to binding of 2'HF with ctDNA. The results reveal that the phenolic moiety is involved in inclusion complexation with β-CD and interaction with DNA. In the presence of β-CD, the phenolic moiety may be included in cyclodextrin cavity, whereas the dihydrobenzopyran-4-one moiety interacts with DNA. Further, β-CD selectively blocks a part of the 2'HF molecule binding with DNA. This renders the remaining portion of the flavanone available for interaction with DNA.