Characterization of folic acid/native cyclodextrins host–guest complexes in solution

• Folic acid dimerizes in aqueous solutions.
• Folic acid forms supramolecular complexes with native (α, β, γ) cyclodextrins.
• 1H NMR, ITC and ESI MS are used for evaluation of association constants.
• The formation of β-cyclodextrin/folic acid complex was studied in physiological buffer.

The complexation of folic acid (FA) with native cyclodextrins was studied and this process was used for the comparison of 1H NMR, ITC and ESIMS for the evaluation of association constants. The stability increases in the series: α-cyclodextrin/FA < γ-cyclodextrin/FA < β-cyclodextrin/FA. 1H NMR and ITC gave comparable results in regard to association constant values, while results obtained for MS were considerably higher due to different interactions (electrostatic instead of hydrophobic) responsible for the stabilization of the complexes. The dimerization of FA in water was also studied, as well as its impact on the process of complexation with native cyclodextrins.

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