Ab initio conformational study of caffeic acid

Abstract

A complete conformational analysis of caffeic acid, a phenolic derivative with well known antioxidant properties, was carried out by ab initio calculations, at the density funtional theory (DFT) level. Fourteen different conformers were obtained, the most stable ones being planar, as the conformational preferences of this molecule were found to be mainly determined by the stabilising effect of p-electron delocalisation. Harmonic vibrational frequencies, as well as potential energy profiles for rotation around several bonds within the molecule, were also calculated. q

Antioxidant phenolic esters with potential anticancer activity: solution equilibria studied by Raman spectroscopy

“…S1, Supporting Information). The present data are also in agreement with the those reported for caffeic [17,19,45,46] and gallic acids, [47] which are well known for yielding stable dimeric structures in the solid phase.…”

Conformational behaviour of biologically active ferulic acid derivatives

“…The present results are in perfect agreement with the ones obtained for cinnamic acid [43] and its analogues, such as hydroxycinnamic acid and its ester or amide derivatives [44][45][46][47][48][49]. In particular, the conformational preferences of naturally occurring hydroxycinnamic acids differing in the ring substitution pattern is strongly dependent on the number, type and relative orientation of these substituents (hydroxyl and/or methoxyl groups).…”

“…In particular, the conformational preferences of naturally occurring hydroxycinnamic acids differing in the ring substitution pattern is strongly dependent on the number, type and relative orientation of these substituents (hydroxyl and/or methoxyl groups). Actually, studies carried out for p-coumaric (4-hydroxycinnamic acid), caffeic (3,4-dihydroxycinnamic acid) [47], ferulic (4-hydroxy-3-methoxycinnamic acid), sinapic (4-hydroxy-3,5-dimethoxycinnamic acid) and 3,4,5-trihydroxycinnamic acids [48] reveal some important differences in these geometrical parameters which may influence their biological (e.g. antioxidant) activity [50][51][52][53][54][55][56].…”

“…However, both geometries should be taken into consideration for structural, chemical and biological studies regarding hydroxycinnamic acids since they are the most populated ones at room temperature. In di-and tri substituted compounds a stabilising intramolecular H-bond is formed, which is known to be energetically favourable in this kind of phenolic systems [44][45][46][47][48][49]57], and is therefore essential for the interpretation of their structure-activity relationships (SAR's).…”

Electrochemical and spectroscopic characterisation of amphetamine-like drugs: Application to the screening of 3,4-methylenedioxymethamphetamine (MDMA) and its synthetic precursors

“…6 (from 100 to 1750 cm −1 ), along with the spectra of their synthetic precursors 3,4-methylene-dioxybenzaldehyde (piperonal) and 3,4-methylenedioxy-␤-methyl-␤-nitrostyrene. The corresponding vibrational wavenumbers were assigned in the light of the theoretical results presently carried out (Table 2) and the spectroscopic data previously reported for ␤-methyl-␤-nitrostyrene derivatives [42][43][44][45] and similar compounds [46][47][48][49][50][51][52].…”