An NMR Study of Capsaicin/β-cyclodextrin Complex

Abstract

Abstract:

NMR spectroscopy was used to investigate the stoichiometry, three-dimensional geometry and formation constant of capsaicin and β-cyclodextrin complex. Capsaicin/β-cyclodextrin solutions with different concentration ratio were measured. Inflection point on Job's curve measured by ¹H NMR appeared at r=0.5. Two-dimensional ROESY and DOSY spectra of the complexes were obtained. Cross peaks in the ROESY spectra appeared between capsaicin H-1 to H-8 and β-cyclodextrin H-3′, H-5′, H-6′. Apparent diffusion coefficients of protons in cyclodextrin and capsaicin were measured with DOSY. The results showed that the stoichiometry of the capsaicin complex was 1∶1 and the isopropyl side of capsaicin entered into the hydrophobic cavity of β-cyclodextrin from the wider rim while H-1 to H-8 of capsaicin were included into the hydrophobic cavity completely. The diffusion coefficient of complex was 2.95×10^-10m²/s.

Key words: NMR, capsaicin, β-cyclodextrin, inclusion effect, ROESY, DOSY

CLC Number:

O482.53

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