Fluorimetric investigation of supramolecular system by modified β-cyclodextrin and its analytical application

The supramolecular interaction of MAH-β-cyclodextrin (MAH-β-CD, a modified β-cyclodextrin carrying seven vinyl carboxylic acid groups) and meferamic acid (MF) has been studied by spectrofluorimetry. The results showed that MAH-β-CD reacted with MF to form a host–guest complex (MAH-β-CD–MF) with stoichiometry (1:1) and the inclusion constant (K = 7.15 × 102 L/mol) was ascertained by the typical double reciprocal plots. From the phase-solubility diagram, an increase in the water solubility of the drug was observed and the apparent stability constant (K1:1) was calculated to be 8.62 × 102 L/mol. Furthermore, the thermodynamic parameters (ΔG°, ΔH° and ΔS°) of MAH-β-CD–MF were obtained and the inclusion mechanism was also preliminarily discussed. In order to further confirm the experimental results, investigation on the molecular modeling was performed. On the basis of the significant enhancement of the fluorescence intensity of MF, a spectrofluorimetric method for MF determination in bulk aqueous solution in the presence of MAH-β-CD was developed. The linear range was 2.00 × 10−8–9.00 × 10−5 mol/L and the detection limit was 3.36 × 10−9 mol/L. The proposed method was successfully applied to determine MF in tablets, serum and urine with the satisfactory result.

Molecular modeling studies were carried out to foresee the possible orientations of MF inside the MAH-β-CD cavity. Optimize structures of the MAH-β-CD/MF complex in two orientations: the benzoic acid moiety inside the MAH-β-CD cavity (a) and the xylyl moiety towards the cavity (b).Figure optionsDownload as PowerPoint slideResearch highlights
► The supramolecular system of MAH-β-CD/MF was the first time investigated by spectrofluorimetry.
► The fluorescence intensity of MAH-β-CD–MF was gradually enhanced with the increasing concentration of MAH-β-CD.
► The inclusion mechanism was understood through the thermodynamic study.
► Molecular modeling studies were consistent with the experimental results.
► A spectrofluorimetric method for the determination of MF in tablets, serum and urine has been developed.