Experimental and Computational Evaluation of Syringic Acid – Structural, Spectroscopic, Biological Activity and Docking Simulation

The single crystal of syringic acid was crystallized by slow evaporation technique and characterized using XRD, FTIR, FT-Raman, and UV-Vis spectroscopy. XRD confirms the crystalline structure as centrosymmetric monoclinic with C2/c space group. The functional groups identified by FTIR and FT Raman studies and by UV-Vis give the cut off wavelength as 276 nm. Quantum chemical calculations were performed using density functional theory. The computed and experimental vibrational wavenumbers were assigned and compared. Frontier molecular orbital research reveals the reactivity and kinetic stability of the molecule. The molecule's reactive site is further confirmed by the Mulliken atomic charge distribution and molecular electrostatic potential surface analysis. The molecule's absorption spectra were computed in the liquid phase (ethanol), by TD-DFT with the same basic set, which established a π to π* electronic transition and was comparable to the observed UV-Vis spectrum. The Hirshfeld analysis was used to determine the effectiveness of interactions between distinct atoms as well as their contribution. The O…H and H…H contributions are highest due to the intermolecular hydrogen bonding. The natural bond orbital analysis demonstrates the molecule's bioactivity. The biological activity such as anti-bacterial, antioxidant and anti-cancer has been evaluated through disk diffusion, DDPH assay and molecular docking method. The zone of inhibition was clearly observed on gram-positive and gram-negative bacterium that showed the anti-bacterial property of syringic acid. The syringic acid prevents breast cancer, according to molecular docking research. Seven different types of breast cancer proteins based on different mechanisms were utilized to test the syringic acid molecule's docking efficiency, and it was revealed that PR and HER-2 have the highest docking scores with −7.7Kcal/mol. In addition, to better understand the safety profile of syringic acid, physicochemical and pharmacokinetic properties were investigated.