DFT and experimental studies of the structure and vibrational spectra of curcumin

Abstract

ABSTRACT:The potential energy surface of curcumin [1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione] was explored with the DFT correlation functional B3LYP method using 6-311G* basis. The single-point calculations were performed at levels up to B3LYP/6-311ϩϩG**//B3LYP/6-311G*. All isomers were located and relative energies determined. According to the calculation the planar enol form is more stable than the nonplanar diketo form. The results of the optimized molecular structure are presented and compared with the experimental X-ray diffraction. In addition, harmonic vibrational frequencies of the molecule were evaluated theoretically using B3LYP density functional methods. The computed vibrational frequencies were used to determine the types of molecular motions associated with each of the experimental bands observed. Our vibrational data show that in both the solid state and in all studied solutions curcumin exists in the enol form.

The Molecular Basis for the Pharmacokinetics and Pharmacodynamics of Curcumin and Its Metabolites in Relation to Cancer

“…1B). The tendency of the keto↔enol equilibrium to shift toward the enol tautomer in these solvent systems has been confirmed experimentally by Fourier transform infrared spectroscopy (FT-IR) (Kolev et al, 2005), nuclear magnetic resonance spectroscopy (NMR) (Roughley and Whiting, 1973;Unterhalt, 1980;Gorman et al, 1994;Khopde et al, 2000), fluorescence spectroscopy (Khopde et al, 2000;Nardo et al, 2008), and absorption spectroscopy (Khopde et al, 2000;Nardo et al, 2008) as well as computationally (Kolev et al, 2005;Balasubramanian, 2006;Payton et al, 2007;Galano et al, 2009). In nonpolar solvents, the steadystate absorption spectra of curcumin in cyclohexane (Nardo et al, 2008), toluene , benzene (Khopde et al, 2000), and others (Tønnesen et al, 1995) exhibit a concrete red band or shoulder, which has been ascribed to the diketo tautomer (Khopde et al, 2000;Nardo et al, 2008Nardo et al, , 2009.…”

pH-controlled Release System for Curcumin based on Functionalized Dendritic Mesoporous Silica Nanoparticles

“…Cur exhibited several peaks, one at 806 cm -1 due to γ(CH) of aromatic and skeletal CCH [57], a band of peaks was observed in region (1000-1300 cm -1 ) which can be attributed to the symmetric and asymmetric configurations of C-O-C chains, peak at 1436 cm -1 was attributed to CH2 bending, while peak at 1502 cm -1 due to C=O and C=C vibration, peak at 1626 cm -1 C=O stretching, peak at 2840 cm -1 was assigned to C-H stretching of methyl group, peak at 3014 cm -1 was due to C-H stretching of aromatic ring, and peak at 3507 cm -1 was attributed to free -OH group vibration [36].…”

The influence of after-treatments on dyeability of raw and bleached cotton with curcumin, and visibility of anthotype produced motifs

“…Razlog za te spremembe je v keto-enolni tavtomeriji kurkumina, saj v nevtralnem ali kislem mediju prevladuje oblika keto, v alkalnem mediju pa enolna oblika [18]. Tovrstno obnašanje molekule je bilo opaženo tudi pri kurkuminu v trdnem stanju [19]. V našem primeru smo tkanino, ki je bila pobarvana s kurkuminom, izpostavili alkalnemu mediju pri pH 10.…”