Preparation and Spectroscopic Characterization of Inclusion Complexes of 3D Ball-Milled Rifampicin with β-cyclodextrin and γ-cyclodextrin 3D Ball-Milled Rifampicin with β-cyclodextrin and γ-cyclodextrin

Rifampicin (RFP) solutions, intended to reduce incidence of prosthetic graft infection, were prepared as three-dimensional ground mixtures (3DGMs) using beta-cyclodextrin (beta CD) and gamma-cyclodextrin (gamma CD) and characterized for their spectroscopic properties and solubility. Phase solubility diagrams revealed that 3DGMs (RFP/beta CD and RFP/gamma CD) produced a complex at 1:1 molar ratio. Pulsed field gradient nuclear magnetic resonance experiments indicated that the diffusion coefficients for RFP/beta CD and RFP/gamma CD were similar to the respective diffusion coefficients for beta CD and gamma CD. Rotating-frame Overhauser effect spectroscopy NMR spectra revealed the existence of a new exchanger peak for RFP/gamma CD, suggesting an intermolecular interaction different from that of RFP/beta CD. Differential scanning calorimetry confirmed the presence of endothermic peak at 191 degrees C indicating the manifestation of RFP in the inclusion complex. Interestingly, molecular interactions from the complexes, RFP/beta CD and RFP/gamma CD, revealed different patterns of inclusion in the 3DGMs. In RFP/beta CD, nuclear Overhauser effect spectroscopy NMR spectra indicated cross peaks for the protons of the methyl group of RFP and the protons (H-5 and H-6) in the beta CD cavity. The methyl group of RFP interacted with the narrow rim of beta CD. With RFP/gamma CD, cross peaks were due to the protons of the methyl group of RFP and the protons of the cavity of gamma CD suggesting multiple inclusion patterns. The observed multiple cross peaks affirm the inclusion of RFP into the CD cavity which enhanced its solubility by 1.6-2.0-fold when prepared as 3DGMs as RFP/beta CD and RFP/gamma CD, respectively.

Automated summary

In this study, Rifampicin solutions were prepared using beta-cyclodextrin and gamma-cyclodextrin, and their spectroscopic properties and solubility were characterized. The results showed that Rifampicin formed complexes with both beta-cyclodextrin and gamma-cyclodextrin, and the different inclusion patterns led to an increase in solubility.