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Structure selective complexation of cyclodextrins with five polyphenols investigated by capillary electrokinetic chromatography
Author(s) -
Zhang QingFeng,
Cheung HonYeung,
Shangguan Xinchen,
Zheng Guodong
Publication year - 2012
Publication title -
journal of separation science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.72
H-Index - 102
eISSN - 1615-9314
pISSN - 1615-9306
DOI - 10.1002/jssc.201200528
Subject(s) - chemistry , taxifolin , cyclodextrin , capillary electrophoresis , enthalpy , syringic acid , molecule , chromatography , stability constants of complexes , organic chemistry , gallic acid , aqueous solution , thermodynamics , physics , flavonoid , antioxidant
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.