Interaction of Non-Steroidal Anti-Inflammatory Drugs, Etoricoxib and Parecoxib Sodium, with Human Serum Albumin Studied by Fluorescence Spectroscopy

Shedding light on the bimolecular interactions of Cafaminol and human serum albumin: spectroscopic characterization and in-silico investigation

Cafaminol, also known as methylcoffanolamine, is a vasoconstrictor and anticatarrhal of the methylxanthine family, which is used as a nasal decongestant. This study aimed to investigate the interaction mechanisms of human serum albumin (HSA) with Cafaminol, through several spectroscopic (fluorescence quenching, UV-visible absorption, and circular dichroism (CD) spectroscopies) and molecular modeling techniques. Stern-Volmer plots were employed to specify the fluorescence quenching mechanism, while the simulation methods were utilized to deduce the approximate binding position of Cafaminol on HSA. On the other hand, thermodynamic parameters, enthalpy and entropy changes, were determined to be, respectively, -105.88 (kJ mol^-1) and -282.34 (J mol^-1 K^-1), using the Van't Hoff equation and analyzed later to specify the main acting forces between Cafaminol and HSA. Overall results revealed the binding of Cafaminol to the site I of HSA, as a result of an enthalpy-driven process, mainly through the van der Waals and hydrogen bonding interactions. Static quenching mechanism was found to be responsible for the fluorescence quenching of HSA in the Cafaminol presence, while the number of binding sites and apparent binding constant were measured accordingly. Docking results proposed that Cafaminol and HSA interact with a binding free energy (ΔG) of -6.5 kcal mol^-1Communicated by Ramaswamy H. Sarma.