Synthesis, Characterization, Molecular Modeling, Binding Energies of Β-Cyclodextrin-inclusion Complexes of Quercetin: Modification of Photo Physical Behavior Upon Β-Cd Complexation

We prepared a naturally occurring flavanoid namely quercetin from tea leaves and analyzed by Absorption, Emission, FT-IR, H-1, C-13 nmr spectra and ESI-MS analysis. The inclusion behavior of quercetin in cyclodextrins like alpha-, beta-, gamma-, per-6-ABCD and mono-6-ABCD cavities were supported such as UV-vis., Emission, FT-IR and ICD spectra and energy minimization studies. From the absorption and emission results, the type of complexes formed were found to depend on stoichiometry of Host:Guest. FT-IR data of CD complexes of quercetin supported inclusion complex formation of the substrate with alpha-, beta- and gamma-CDs. The inclusion of host-guest complexation of quercetin with alpha-, beta-, gamma-CDs, per-6-ABCD and mono-6-ABCDs provides very valuable information about the CD:quercetin complexes, the study also shows that beta-CD complexation improves water solubility, chemical stability and bioavailability of quercetin. Besides, phase solubility studies also supported the formation of 1:1 drug-CD soluble complexes. All these spectral results provide insight into the binding behavior of substrate into CD cavity in the order per-6-ABCD > Mono-6-ABCD > gamma-CD > beta-CD > alpha-CD. The proposed model also finds strong support from the fact with excess CD this exciton coupling disappears indicates the formation of only 1:1 complex.