Photoprotection of 1,4-dihydropyridine derivatives by dyes

Furthermore, our attention was focused on determination the role of the selected dyes during the photodegradation of nisoldipine and the calculations were made to eliminate an inner filter effect. The values obtained were used to construct a Stern-Volmer plot and calculate the Stern-Volmer constants (KSV). On the basis of the KSV and the values of the quenching constant (kq) the exited state lifetime (τo) of nisoldipine in the presence of indigotine and azorubine were estimated. The calculated values of τo for NS were 6.66 × 10−6 s - in the presence of indigotine and 2.76 × 10−6 s - in the presence of azorubine, indicating that the photodegradation of nisoldipine occurs from the lowest triplet excited state.