Abstract
Praziquantel (PZQ) is a biopharmaceutical classification system (BCS) class II anthelmintic drug characterized by poor solubility and a bitter taste, both of which can be addressed by inclusion complexation with cyclodextrins (CD). In this work, a comprehensive investigation of praziquantel/cyclodextrin (PZQ/CD) complexes was conducted by means of UV–vis spectroscopy, spectrofluorimetry, NMR spectroscopy, liquid chromatography-high-resolution mass spectrometry (LC-HRMS/MS), and molecular modeling. Phase solubility studies revealed that among four CDs tested, the randomly methylated β-CD (RMβCD) and the sulfobutylether sodium salt β-CD (SBEβCD) resulted in the highest increase in PZQ solubility (approximately 16-fold). The formation of 1:1 inclusion complexes was confirmed by HRMS, NMR, and molecular modeling. Both cyclohexane and the central pyrazino ring, as well as an aromatic part of PZQ are included in the CD central cavity through several different binding modes, which exist simultaneously. Furthermore, the influence of CDs on PZQ stability was investigated in solution (HCl, NaOH, H2O2) and in the solid state (accelerated degradation, photostability) by ultra-high-performance liquid chromatography–diode array detection–tandem mass spectrometry (UPLC-DAD/MS). CD complexation promoted new degradation pathways of the drug. In addition to three already known PZQ degradants, seven new degradation products were identified (m/z 148, 215, 217, 301, 327, 343, and 378) and their structures were proposed based on HRMS/MS data. Solid complexes were prepared by mechanochemical activation, a solvent-free and ecologically acceptable method.
Highlights
Praziquantel (PZQ) is an anthelmintic drug widely used in developing countries to treat schistosomiasis, a neglected tropical disease caused by parasitic blood flukes of the Schistosoma genus.[1]
Solubility studies of PZQ with selected CDs were investigated in water using liquid chromatography, UV− vis absorption spectroscopy, and fluorescence spectroscopy
A monohydroxylated structure was suggested for degradation product relative retention times (RRT) 1.10 (m/z 329), which was only detected for the PZQ/HPβCD complex, based on observed fragments and previously reported data.[36−38] The fragment ion m/z 311 would correspond to the loss of water; it was not detected in MS/MS spectra possibly due to the high fragmentation of the parent ion
Summary
Praziquantel (PZQ) is an anthelmintic drug widely used in developing countries to treat schistosomiasis, a neglected tropical disease caused by parasitic blood flukes of the Schistosoma genus.[1]. In our previous study, which aimed to develop new, solvent-free, and ecologically more acceptable methods for the preparation of PZQ/CD complexes in the solid state, we noticed an unfavorable effect of the inclusion complex formation on the chemical stability of the drug.[12] This prompted us to thoroughly investigate the effect of CDs on the chemical stability of PZQ, as this issue has not been systematically investigated so far. The results obtained in this investigation will enable a critical evaluation of the applicability of CDs in the development of novel PZQ formulations with improved functionality
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