Molecular encapsulation of berberine by a modified β-cyclodextrin and binding of host: guest complex to G-quadruplex DNA.

The capacity to control quadruplex formation, especially in cancer cells, is captivating and entails a reasonable comprehension of the ligand-G-quadruplex binding. Herein, we report an iminopyrenyl-β-cyclodextrin conjugate interacting with duplex and G-quadrulex DNAs. In addition, the host: guest association of the established G-quadruplex binder, berberine, with the β-cyclodextrin derivative is studied employing 2-D ROESY. NMR, UV-visible, and fluorescence spectroscopic techniques are utilized to explore the β-cyclodextrin conjugate's interaction with the quadruplexes. The Binding constants are accounted for the association of the ligands to each of the DNAs viz., calf thymus DNA (duplex), , , and (quadruplexes). The modulation of the iminopyrenyl-β-cyclodextrin binding to the DNAs are observed when berberine is loaded in the host molecule. A vivid distinction between the interactions of the ligands with duplex and quadruplex structures is inferred. Berberine-loaded iminopyrenyl-β-cyclodextrin shows a higher affinity for binding to .