Complexation study of diclofenac with beta-cyclodextrin and spectrofluorimetric determination

Area of Science:

• Pharmaceutical Chemistry
• Supramolecular Chemistry
• Analytical Chemistry

Background:

• Diclofenac is a widely used non-steroidal anti-inflammatory drug (NSAID).
• Beta-cyclodextrin (beta-CD) is a cyclic oligosaccharide known for its ability to form inclusion complexes with various molecules.
• Understanding the interaction between diclofenac and beta-CD is crucial for potential drug delivery and analytical applications.

Purpose of the Study:

• To investigate the inclusion complexation between diclofenac and beta-cyclodextrin.
• To characterize the stoichiometry and stability of the diclofenac-beta-CD complex.
• To develop and validate a spectrofluorimetric method for diclofenac determination in the presence of beta-CD.

Main Methods:

• Potentiometry, spectrophotometry, and spectrofluorimetry were employed to study complexation.
• 1H NMR spectroscopy and AM1 semiempirical calculations were used for structural characterization.
• Spectrofluorimetric analysis was performed to develop a quantitative method for diclofenac.

Main Results:

• A 1:1 stoichiometry was determined for the diclofenac-beta-CD inclusion complex in both acidic and neutral pH.
• Equilibrium constants for complexation were found to be in the order of 10^3, indicating moderate stability.
• Analysis of pKa values suggested the carboxylic group of diclofenac is located outside the beta-CD cavity.
• The developed spectrofluorimetric method achieved improved limits of detection (0.03 µg/mL) and quantification (0.1 µg/mL) in the presence of beta-CD.
• The method was successfully applied to quantify diclofenac in pharmaceutical preparations.

Conclusions:

• Diclofenac forms a stable 1:1 inclusion complex with beta-cyclodextrin.
• The complexation influences the pKa of diclofenac, with the carboxylic group likely external to the beta-CD cavity.
• The presence of beta-CD significantly enhances the spectrofluorimetric determination of diclofenac, offering a sensitive method for pharmaceutical analysis.