Photodegradation studies of 1,4-dihydropyridine compounds by MCR analysis on UV spectral data

Background: 1,4-Dihydropyridines (DHPs) are well-known light-sensitive compounds. Photostability studies are necessary to ensure safety in therapy.

Materials & methods: Photodegradation experiments on 15 condensed DHP derivatives were made according to the International Conference on Harmonization rules. Degradation profiles were monitored by spectrophotometry and the data were processed by multivariate curve resolution analysis.

Results: The analysis of the spectral data showed the formation of a single photoproduct from two DHPs, due to the aromatization of the pyridine ring. Traces of a second photoproduct were revealed in 12 DHPs and a third photoproduct was verified only in one case.

Conclusion: DHPs showed high stability when fluorine was in the position R1 of the phenyl ring or simultaneously present in R1 and R2 positions. In contrast, the presence of chlorine in R1 or R2 strongly increased the degradation.