Structure selective complexation of cyclodextrins with five polyphenols investigated by capillary electrokinetic chromatography

Abstract

The complexation of five polyphenols, namely trans-resveratrol, astilbin, taxifolin, ferulic acid, and syringic acid (guest molecules) with α-, β-, and γ-cyclodextrin (host molecules), was investigated by capillary electrokinetic chromatography. The binding constants were calculated based on the effective electrophoretic mobility change of guests with the addition of cyclodextrins into the background electrolyte. Because of cavity size, cyclodextrins showed structure-selective complexation property to different guest. The stability of the trans-resveratrol complexes was in the order of β- > α- > γ-cyclodextrin. The cavity size of α-cyclodextrin was too small for astilbin and taxifolin molecules, and thus they could not form complexes. The molecular size of syringic acid was too big for all cyclodextrins cavity, and no cyclodextrin could form complexes with it. Temperature studies showed that the binding constants decreased with the rise of temperature. Enthalpy and entropy values were calculated and the negative values of these parameters indicated that the complexation process was enthalpy-controlled. Van der Waals force and release of high-enthalpy water molecules from the cyclodextrins cavity played important roles in the process.

Hydroxypropyl-β-Cyclodextrin as a Green Co-Solvent in the Aqueous Extraction of Polyphenols from Waste Orange Peels

“…Increases in T have been explicitly demonstrated to increase the aqueous solubility of sparingly soluble polyphenols in the presence of various cyclodextrins [39]. On the other hand, it was found that the binding constants of certain polyphenol complexes with α-, β-, and γ-cyclodextrin decreased as T increased [40]. Results on the interactions of the stilbene (E)-piceatannol with HP-β-CD were in concurrence, illustrating a decrease in the complexation constant as a response to increasing T [41].…”

Thermodynamic parameters for the complexation of water-soluble betulin derivatives with (2-hydroxypropyl)-β-cyclodextrin determined by affinity capillary electrophoresis

“…To determine stability constants and thermodynamic parameters, a number of techniques are used [6,7], including UV-Vis [8][9][10] and fluorescence [8,9,11] spectroscopy, conductometry [12,13], isothermal calorimetry [14][15][16][17], phase solubility study with UV-Vis spectroscopy [14,18,19] or high-performance liquid chromatography [20], potentiometry [21], capillary electrophoresis [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39], and other techniques. Capillary electrophoresis (CE) has advantages such as rapidity, high selectivity, a small value of samples, and low-cost of analysis.…”

Pillarene functionalized polymer monolithic column for the solid-phase microextraction preconcentration of parabens

“…32 On the other hand, synthetic macrocyclic host compounds, [33][34][35][36][37][38] such as crown ethers, cyclodextrins, calixarenes, and cucurbiturils, play important roles in supramolecular chemistry and nanoscience, and receive considerable attention as adsorption materials in recent years. [39][40][41][42] Pillarenes (or pillararenes), 43 a new class of supramolecular hosts which were rstly synthesized in 2008, 44 have become one of the most popular topics in supramolecular chemistry. [45][46][47][48][49][50][51][52][53][54][55][56][57][58] Recently, we successfully employed carboxylatopillar [5]arenes (CP [5]As) 59 as sorbent materials, either by functionalizing them on the surface of Fe 3 O 4 magnetic nanoparticles via covalent bonds for the extraction and detection of pesticides 60 or by packing them in a glass microcolumn for the separation and preconcentration of trace gold and palladium via ow injection ame atomic absorption spectrometry.…”