Solvatochromic Effects, Photophysical Properties, Fluorescence Quenching, and Molecular Docking of Ferulic and Sinapic Acids: Experimental and Computational Approaches

Abstract

Ferulic and sinapic acids are common hydroxycinnamic acids known for their strong antioxi dant properties and potential health benefits. This study investigated the Solvatochromic effects, photophysical properties, fluorescence quenching, and molecular docking of FA and SA. The Solvatochromic effect analysis revealed that the solvent polarity significantly affected the emission spectra compared with the absorption spectra of FA and SA. The change in the ground and excited dipole moments was calculated using various models, with the Lippert–Mataga method showing the largest change due to the exclusion of so lute–solvent interactions and solute polarizability. Analysis of UV–Vis and fluorescence spectra demonstrated that solvent polarity and concentration significantly affected the op tical transition properties, including the integrated absorption cross-section, oscillator strength, integrated absorption coefficient, Einstein coefficients (A and B), and transition dipole moment. Furthermore, the interaction between solvent and FA or SA influenced key photophysical parameters, such as fluorescence quantum yield, radiative and nonradiative decay rates, and fluorescence lifetime. The fluorescence quenching experiments revealed that CF induced static quenching of FA and SA fluorescence, resulting in the formation of nonfluorescent complexes. The van’t Hoff equation showed that the FA–CF interactions were primarily governed by electrostatic forces, while the SA–CF interactions were influenced by van der Waals forces and hydrogen bonding. The negative Gibbs free energy further confirmed the spontaneity of these interactions. Conformational changes in the FTIR spectra of FA and SA detected upon binding to CF. Quantum chemical calculations revealed that increasing the temperature increased the enthalpy, entropy, and heat capacity, suggesting potential molecular instability. The solvent polarity affected the thermodynamic parameters, dipole moments, HOMO–LUMO energy gaps, and chemical reactivity descriptors. The excited-state dipole moments were larger than those of the ground state using computational method, confirming the experimental results. TDDFT analysis revealed redshifts in both the absorption and emission spectra, which align with the experimental findings. Molecular docking revealed FA–CF and SA–CF interactions, validating the fluorescence quenching and linking these interactions to anticancer properties by binding to anticancer proteins.