Application of a self-modeling curve resolution method for studying the photodegradation kinetics of nitrendipine and felodipine

Dihydropyridine (DHP) derivatives, as calcium channel blockers with cardiovascular activity, are highly photosensitive and converted in the presence of light to compounds that are inactive. In this work, a self-modeling curve resolution method was applied to study the photodegradation kinetics of nitrendipine and felodipine by spectrophotometric method. The methanolic solutions of drugs were separately exposed to UV and daylight, respectively. A fully soft-modeling multivariate curve resolution method based on the combination of iterative target transformation and Kubista methods were used to analyze the recorded absorbance data, extracting the concentration profiles and pure spectra of the drugs and their photodegradation products. By fitting the concentration profiles of the studied DHP drugs to different kinetic equations, it was found that at the beginning of lighting, the reaction is zero-order and in the case of nitrendipine it changes to a first-order kinetic when the concentration of products exceeded than that of the initial compounds.