Substituent effect of side chains on the photochemical behavior of a new generation 1,4-dihydropyridine: Lercanidipine

Lercanidipine (LERCA) is a third generation antihypertensive drug belonging to the 1,4-dihydropyridine's family, which has been reported to induce photoallergic and/or phototoxic effects in patients with long term treatment. The electronic nature of substituents on the 4-aryl moiety bonded to the 1,4-dihydropyridine ring has been described to strongly affect the photophysical and photochemical behavior of this family of compounds, which displays a typical absorption band around 360 nm. LERCA undergoes photodegradation after excitation, with a first order kinetic, in significant competition to the radiative path. The photodegradation quantum yields for LERCA are higher than for its homologue nimodipine (NIMO), thus indicating that the substituents on the 1,4-dihydropyridinic ring also affect their photophysical and photochemical properties. The media where the photodegradation takes place impacts on the product profile, in a homogeneous one the photoproducts obtained appear to be more polar than those obtained for a micro-heterogeneous one (micelles or bilayers mimicking biological media).