Water-induced isomerism of salicylaldehyde and 2-acetylpyridine mono- and bis-(thiocarbohydrazones) improves the antioxidant activity: spectroscopic and DFT study
| Autor: | Mohamed H. Assaleh, Milena D. Milošević, Aleksandar D. Marinković, Ilija N. Cvijetić, Milena Simic, Snežana Bjelogrlić, Aleksandra R. Božić |
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| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
Radical
010402 general chemistry 01 natural sciences Medicinal chemistry Spindensity distribution chemistry.chemical_compound Bond dissociation enthalpy Bonddissociationenthalpy Antioxidant activity Molecule Thiocarbohydrazones Antioxidantactivity Physical and Theoretical Chemistry Z isomerism Spin density distribution 010405 organic chemistry Chemistry Hydrogen bond E/Z isomerism Nuclear magnetic resonance spectroscopy Condensed Matter Physics Tautomer 0104 chemical sciences Salicylaldehyde Intramolecular force Isomerization Tautomerism |
| Zdroj: | Structural Chemistry |
| Popis: | Thiocarbohydrazones (TCHs) and structurally related molecules are versatile organic compounds which exert antioxidant, anticancer, and other beneficial health effects. The combination of UV/Vis, NMR spectroscopy, and quantum chemical calculations was used to rationalize the experimentally observed increase in the radical scavenging activity upon the addition of water in DMSO solution of TCHs. Mono- and bis(salicylaldehyde) TCHs (compounds 1 and 2) undergo water-induced E-to-Z isomerization which is followed by disruption of intramolecular hydrogen bond, ground state destabilization, and 11 kcal/mol decrease in the bond dissociation enthalpy (BDE). Electron spin delocalization is more pronounced in Z-isomers of 1 and 2. On the other hand, 2-acetylpyridine TCHs (compounds 3 and 4) undergo thione-to-thiol tautomerism which also decreases the BDE and facilitates the hydrogen atom transfer to 2,2-diphenyl-1-picrylhydrazyl radical (DPPH∙). The appearance of thiolic –SH group as another reactive site toward free radicals improves the antioxidant activity of 3 and 4. The spin density of 3- and 4-thiol radicals is delocalized over the entire thiocarbohydrazide moiety compared to more localized spin of thione radicals. Additional stabilization of thiol radicals corroborates with the increased antioxidant activity. This study provides the new insights on the solution structure of TCHs, and also highlights the importance of solution structure determination when studying the structure-antioxidant relationships of isomerizable compounds. Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/3848] |
| Databáze: | OpenAIRE |
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