Complexation of capsaicin with hydroxypropyl-β-cyclodextrin and its analytical application

Area of Science:

• Analytical Chemistry
• Physical Chemistry
• Materials Science

Background:

• Capsaicin, the active compound in chili peppers, has various applications but limited aqueous solubility.
• Cyclodextrins, particularly hydroxypropyl-β-cyclodextrin (HPβCD), are widely used to improve the solubility and bioavailability of guest molecules.

Purpose of the Study:

• To investigate the host-guest inclusion complexation between HPβCD and capsaicin.
• To develop a sensitive and accurate spectrofluorimetric method for capsaicin quantification.

Main Methods:

• Spectroscopic analysis (fluorescence, 1H NMR)
• Thermal analysis (thermoanalysis)
• Molecular modeling
• Job's plot analysis
• Phase solubility studies
• Spectrofluorimetric assay development

Main Results:

• A 1:2 stoichiometry (HPβCD:capsaicin) was confirmed for the inclusion complex.
• The apparent stability constant of the complex was determined to be 3.76 × 10^6 M^-2.
• Complexation with HPβCD significantly enhanced capsaicin's fluorescence.
• A spectrofluorimetric method was developed with linearity from 0.05-60 μg/mL and a low detection limit of 0.04 μg/mL.
• The method demonstrated high accuracy and precision, with a relative standard deviation of 1.30% and satisfactory recovery (99.5-105.6%) in chili powder analysis.

Conclusions:

• HPβCD effectively forms an inclusion complex with capsaicin, improving its properties.
• The developed spectrofluorimetric method is suitable for accurate and sensitive determination of capsaicin in complex matrices like chili powder.