Interaction of capsaicin with calf thymus DNA: A multi-spectroscopic and molecular modelling study

Studying the mode of interaction between small molecules and DNA has received much attention in recent years, as many drugs have been reported to directly interact with DNA thereby regulating the expression of many genes. Capsaicin is a capsaiciniods family phytocompound having many therapeutic applications including diabetic neuropathy, rheumatoid arthritis, prevention of DNA strand breaks and chromosomal aberrations. In this study, we have investigated the interaction of capsaicin with calf thymus DNA using a number of biophysical techniques to get an insight and better understanding of the interaction mechanism. Analysis of UV-vis absorbance spectra and fluorescence spectra indicates the formation of complex between capsaicin and Ct-DNA. Thermodynamic parameters ΔG, ΔH, and ΔS measurements were taken at different temperatures indicated that hydrogen bonding and van der Waal's forces played major role in the binding process. Additional experiments such as iodide quenching, CD spectroscopy suggested that capsaicin possibly binds to the minor groove of the Ct-DNA. These observations were further confirmed by DNA melting studies, viscosity measurements. Molecular docking provided detailed computational interaction of capsaicin with Ct-DNA which proved that capsaicin binds to Ct-DNA at minor groove. Computational molecular docking also revealed the exact sites and groups to which capsaicin interacted.