In-Vitro Study of the Binding of Atorvastatin with Adenine using Multi-Spectroscopic Approaches

Atorvastatin-an oral lipid regulating drug is a competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase), which is the rate determining enzyme for cholesterol synthesis. Adenine is a purine nucleobase that is found in deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) to generate genetic information. The binding mechanism of atorvastatin and adenine was studied for the first time utilizing various techniques, including UV-visible spectrophotometry, spectrofluorimetry, synchronous fluorescence spectroscopy (SF), Fourier transform infrared (FTIR), fluorescence resonance energy transfer (FRET), and metal ion complexation. The fluorescence spectra of the complex indicated that atorvastatin is bound to adenine via hydrophobic interaction through a spontaneous binding process, and the fluorescence quenching mechanism was found to be static quenching with a binding constant of 1.4893 × 10⁴ Lmol^-1 at 298 K. Various temperature settings were used to investigate thermodynamic characteristics, such as binding forces, binding constants, and the number of binding sites. The interaction parameters, including the standard enthalpy change (ΔH^ο) and standard entropy change (ΔS^ο) were calculated using Van't Hoff's equation to be 42.82 kJmol^-1 and 208.9 Jmol^-1K^-1, respectively. The findings demonstrated that the adenine- atorvastatin binding was endothermic. Furthermore, the results of the experiments revealed that some metal ions (K⁺, Ca⁺², Co⁺², Cu⁺², and Al⁺³) facilitate the binding interaction between atorvastatin and adenine. Slight changes are observed in the FTIR spectra of adenine, indicating the binding interaction between adenine and atorvastatin.