Insights in the radical scavenging mechanism of syringaldehyde and generation of its anion

• Published in: Journal of molecular structure Vol. 1108; pp. 552 - 559
• Main Authors: Yancheva, D., Velcheva, E., Glavcheva, Z., Stamboliyska, B., Smelcerovic, A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.03.2016
• Subjects: Anion; Anions; Antioxidants; Computation; DFT; Enthalpy; Free radicals; Mathematical analysis; Radicals; Scavenging; Structure; Syringaldehyde; Vibrational spectra; Syringaldehyde; DFT; Structure; Anion; Vibrational spectra
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2015.12.054

The ability of syringaldehyde, a naturally occurring phenolic antioxidant and medicinally important compound, to scavenge free radicals according different mechanisms was elucidated by computing the respective reaction enthalpies at DFT B3LYP/6-311++G** level. Bond dissociation enthalpy, ionization potentials and proton affinities were calculated in gas phase, benzene, water and DMSO in order to account for different environment (nonpolar lipid membranes and polar physiological liquids) where the antioxidant action in the living organism could take place and various experimental in vitro conditions. Molecular and electronic properties influencing the reactivity of syringaldehyde according to the different mechanisms were discussed in the light of the reported radical scavenging activities in crocin bleaching, oxidation potential of the first anodic peak and DPPH test. According to the calculated reaction enthalpies, in polar environment the syringaldehyde reacts preferably by sequential proton loss electron transfer which is related to the formation of a phenoxy anion. Such phenoxy anion was generated in DMSO solution and the changes in the force field, steric and electronic structure, resulting from the conversion, were described in detail based on the IR spectral data and DFT computations. [Display omitted] •Syringaldehyde is natural phenolic antioxidant and medicinally important compound.•Radical scavenging mechanism of syringaldehyde was studied by DFT calculations.•The respective anion, intermediate in SPLET mechanism, was generated.•The spectral and structural changes caused by the conversion were described.