Physicochemical Study of the Complexation of Pterostilbene by Natural and Modified Cyclodextrins

Abstract

In this paper, the interaction between pterostilbene and cyclodextrins (CDs) is described for the first time using steady-state fluorescence. It was seen that pterostilbene forms a 1:1 complex with all of the natural (alpha-, beta-, and gamma-CDs) and modified (HP-beta-CD, methyl-beta-CD, and ethyl-beta-CD) CDs tested. Among natural CDs, the interaction of pterostilbene with beta-CD was the most efficient. However, all of the modified CDs showed higher complexation constants (K(F)) than beta-CD. The highest K(F) was found for HP-beta-CD (17520 +/- 981 M(-1)), in which its value showed a strong dependence upon pH in the region where the pterostilbene begins the deprotonation of its hydroxyl group. Moreover, the values of K(F) decreased as the system temperature increased. To obtain information on the mechanism of pterostilbene affinity for CD, the thermodynamic parameters of the complexation (DeltaH degrees , DeltaS degrees , and DeltaG degrees ) were studied. Finally, a comparison of the K(F) values obtained for three types of stilbenes revealed that both the stoichiometry and the K(F) values of the complex are dependent upon the structure of the guest molecule. While the trans-resveratrol-HP-beta-CD and pterostilbene-HP-beta-CD complexes showed a 1:1 stoichiometry with a higher K(F) value for the trans-resveratrol-HP-beta-CD complexes, trans-stilbene showed a 1:2 stoichiometry.

Use of reversed phase high pressure liquid cromatography for the physicochemical and thermodynamic characterization of oxyresveratrol/β-cyclodextrin complexes

“…The fact that ␤-CD was the optimum natural CD for complexing oxyresveratrol is in good agreement with the results of most of papers which compare the complexation of several stilbenoids compounds with natural CDs [7][8][9][10][11].…”

“…Although several authors have claimed that stilbenes can not form CD complexes with a 1:2 stoichiometry, López-Nicolás et al [10] demonstrated that trans-stilbene can able to be complexed by two molecules of HP-␤-CD. For this reason, we studied the possible formation of a 1:2 oxyresveratrol/␤-CD complex via a pre- cursor 1:1 complex (Fig.…”

“…Although CDs form complexes with resveratrol [7][8][9], pterostilbene [10] and pinosylvin [11] with a 1:1 stoichiometry, López-Nicolás et al [10] showed that trans-stilbene forms 1:2 complexes with HP-␤-CD. For this reason, and because this is the first study where the interaction of oxyresveratrol with ␤-CD is studied, it was necessary to investigate the stoichiometry for ␤-CD complexes of oxyresveratrol.…”

“…In recent years, different stilbenoids with high antioxidant activity such as resveratrol, pterostilbene and pinosylvin have been complexed by natural and modified CDs [7][8][9][10][11]. However, to date, no research about the complexation of oxyresveratrol, one of the most potent antioxidants known, with CDs has been published.…”

Spectroscopic characterization of the inclusion complexes of luteolin with native and derivatized β-cyclodextrin

“…As shown in Table 1, we can note, that the stability constant for LU-HPbCD and LU-DMbCD complexes decrease with increasing temperature as expected for an exothermic process, which might be interpreted as a lower degree of interaction at higher temperatures, possibly due to the fact that hydrogen bonds are usually weakened by heating. 23 However, for LU-bCD, stability constant increase as temperature rises, as expected for an endothermic process. These temperature effects on the association constant were also found for galangin-cyclodextrin complexes.…”