Abstract
The oxidation of lomefloxacin (LOM) and balofloxacin (BAL) under the influence of azo initiator of radical reactions of 4,4′-azobis(4-cyanopentanoic acid) (ACVA) and H2O2 was examined. Oxidation using H2O2 was performed at room temperature while using ACVA at temperatures: 40, 50, 60 °C. Additionally, the oxidation process of BAL under the influence of KMnO4 in an acidic medium was investigated. New stability-indicating HPLC methods were developed in order to evaluate the oxidation process. Chromatographic analysis was carried out using the Kinetex 5u XB—C18 100A column, Phenomenex (Torrance, CA, USA) (250 × 4.6 mm, 5 μm particle size, core shell type). The chromatographic separation was achieved while using isocratic elution and a mobile phase with the composition of 0.05 M phosphate buffer (pH = 3.20 adjusted with o-phosphoric acid) and acetonitrile (87:13 v/v for LOM; 80:20 v/v for BAL). The column was maintained at 30 °C. The methods were validated according to the ICH guidelines, and it was found that they met the acceptance criteria. An oxidation process followed kinetics of the second order reaction. The most probable structures of LOM and BAL degradation products formed were assigned by the UHPLC/MS/MS method.
Highlights
The stability of drugs is the one of the basic requirements, which is closely related to the efficiency of pharmacological action and safety of therapy
The solutions of the tested FQs after 48 h of incubation at 50 ◦ C in 10 mM ACVA, after 72 h incubation in 3% H2 O2 and after 1 h of incubation in acidic medium with the presence of KMnO4 were used for the analysis
The oxidation reactions in the presence of ACVA, H2 O2, and KMnO4 followed the kinetics of the second-order reactions
Summary
The stability of drugs is the one of the basic requirements, which is closely related to the efficiency of pharmacological action and safety of therapy. Changes in the structure of a chemical compound and physicochemical properties may lead to a decrease in the therapeutic value of the drug through disturbances in the absorption process or a decrease in pharmacological activity or even increase in its toxicity. The chemical stability of pharmaceutical substances is a significant problem that affects the safety and efficiency of the pharmaceutical preparation. The stability of the pharmaceutical active substance can be tested by stress tests, long-term, intermediate, and accelerated stability studies [1]. Oxidation reactions are one of the two most common mechanisms of drug degradation in pharmaceutical systems [2,3,4]. The reactions are typically autoxidative and its mechanism consists of Molecules 2020, 25, 5251; doi:10.3390/molecules25225251 www.mdpi.com/journal/molecules
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