Preparation and characterisation of ethambutol with β-cyclodextrin: a comprehensive molecular insight into host–guest interaction

The increase in new cases of drug resistance to first-line drugs such as ethambutol (ETB) makes it necessary to develop improvements for antituberculosis drugs. A new method for improving the bioavailability of active pharmaceutical ingredient (API) was investigated for preventing drug resistance and side-effects of antituberculosis drugs. In this study, an antituberculosis drug delivery system using β-cyclodextrin (β-CD) as the supramolecular carrier of ETB was prepared using the kneading method. The inclusion behaviour of β-CD/ETB inclusion complex in solid and liquid state was investigated. The inclusion complex was characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, nuclear magnetic resonance (NMR) spectroscopy, and UV–visible spectroscopy. The (1)H and nuclear Overhauser effect spectroscopy NMR results indicated the hydrophobic interaction between β-CD and ETB. Meanwhile, the Benesi-Hildebrand equation was used to calculate the formation constant (K) of β-CD/ETB complex in natural condition, pH4, and pH9, which were 105.43, 107.06, and 119.11, respectively. The stoichiometry ratio of β-CD/ETB complex was proven to be 1:1.