Host-guest system of Vitamin B10 in β-cyclodextrin: characterization of the interaction in solution and in solid state

Conventional drugs are usually formulated for the immediate release of the medicinal substances and for obtaining the desired therapeutic effect. The aim of this paper was to investigate the possible interactions between Vitamin B10 and beta-cyclodextrin (beta-CD), to determine the physical-chemical characteristics and the interactions present in the corresponding inclusion compound. The so-obtained compounds were characterized by X-ray diffraction, DSC and FTIR spectroscopy. H-1 NMR and UV-vis spectroscopic methods were employed to study the inclusion process in aqueous solution. The X-ray powder diffraction patterns demonstrate the inclusion compound formation, especially for the lyophilized product where the amorphous phase dominates. The existence of the inclusion compounds obtained by different methods was confirmed by comparing with DSC and FTIR data of the pure compounds and the (1:1) Vitamin B10:beta-CD physical mixture (pm). H-1 NMR measurements on aqueous solutions of Vitamin B10 and beta-CD in D2O allowed us to establish the corresponding Vitamin B10's and cyclodextrin's protons implied in the complexation process. 2D NMR spectroscopy established the geometry of the inclusion complex. H-1 NMR, UV-Vis and fluorescence data were used to obtain the stoichiometry and the stability constant of the complex.