title: The effect of the water on the curcumin tautomerism: a quantitative approach.
abstract: The tautomerism of curcumin has been investigated in ethanol/water binary mixtures by using UV-Vis spectroscopy and advanced quantum-chemical calculations. The spectral changes were processed by using advanced chemometric procedure, based on resolution of overlapping bands technique. As a result, molar fractions of the tautomers and their individual spectra have been estimated. It has been shown that in ethanol the enol-keto tautomer only is presented. The addition of water leads to appearance of a new spectral band, which was assigned to the diketo tautomeric form. The results show that in 90% water/10% ethanol the diketo form is dominating. The observed shift in the equilibrium is explained by the quantum chemical calculations, which show that water molecules stabilize diketo tautomer through formation of stable complexes. To our best knowledge we report for the first time quantitative data for the tautomerism of curcumin and the effect of the water.
authors: Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bldg. 9, 1113 Sofia, Bulgaria.
authors: Yana
authors: Y
authors: Manolova
authors: Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bldg. 9, 1113 Sofia, Bulgaria.
authors: Vera
authors: V
authors: Deneva
authors: Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bldg. 9, 1113 Sofia, Bulgaria. Electronic address: lantonov@orgchm.bas.bg.
authors: Liudmil
authors: L
authors: Antonov
authors: Faculty of Pharmacy, Medical University - Sofia, 2 Dunav Str., 1000 Sofia, Bulgaria.
authors: Elena
authors: E
authors: Drakalska
authors: Faculty of Pharmacy, Medical University - Sofia, 2 Dunav Str., 1000 Sofia, Bulgaria.
authors: Denitsa
authors: D
authors: Momekova
authors: Faculty of Pharmacy, Medical University - Sofia, 2 Dunav Str., 1000 Sofia, Bulgaria.
authors: Nikolay
authors: N
authors: Lambov
mesh_terms: D003474:Curcumin / Q000737:chemistry*; D008968:Molecular Conformation; D012997:Solvents / Q000737:chemistry; D013057:Spectrum Analysis; D013237:Stereoisomerism; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D012997:Solvents; D014867:Water; D003474:Curcumin
keywords: Chemometrics; Curcumin; DFT; Tautomerism; UV–Vis spectroscopy; Water effect