A biophysical approach to study the impact of muscle relaxant drug tizanidine on stability and activity of serum albumins.

The binding affinity of a drug with carrier proteins plays a major role in the distribution and administration of the drug within the body. Tizanidine (TND) is a muscle relaxant having antispasmodic and antispastic effects. Herein, we have studied the effect of tizanidine on serum albumins by spectroscopic techniques, such as absorption spectroscopic analysis, steady, state fluorescence, synchronous fluorescence, circular dichroism, and molecular docking. The binding constant and number of binding sites of TND with serum proteins were determined by means of fluorescence data. The thermodynamic parameters, like Gibbs' free energy (ΔG), enthalpy change (ΔH), and entropy change (ΔS), revealed that the complex formation is spontaneous, exothermic, and entropy driven. Further, synchronous spectroscopy revealed the involvement of Trp (amino acid) responsible for quenching of intensity in fluorescence in serum albumins in presence of TND. Circular dichroism results suggest that more folded secondary structure of proteins. In BSA the presence of 20 µM concentration of TND was able to gain most of its helical content. Similarly, in HSA the presence of 40 µM concentration of TND has been able to gain more helical content. Molecular docking and molecular dynamic simulation further confirm the binding of TND with serum albumins, thus validating our experimental results.