Evidences of cyclodextrin-mediated enantioselective photodegradation of rac-nicardipine by capillary electrophoresis

✍ Scribed by Romeo Pomponio; Roberto Gotti; Carlo Bertucci; Vanni Cavrini

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 110 KB
• Volume: 22
• Category: Article
• ISSN: 0173-0835
• DOI: 10.1002/1522-2683(200109)22:15<3243::aid-elps3243>3.0.co;2-8

✦ Synopsis

Evidences of cyclodextrin-mediated enantioselective photodegradation of rac-nicardipine by capillary electrophoresis Capillary electrophoresis (CE) was applied to photostability studies on rac-nicardipine, a dihydropyridine chiral drug. CE methods were developed able to provide the enantioresolution of drug and its separation from the photodegradation products. Enantioresolution was achieved using 5% sulfated-b-cyclodextrin (S-b-CD) as chiral selector in 20 mM triethanolammonium phosphate solution (pH 3). The photostability studies were carried out on inclusion complexes of rac-nicardipine with b-cyclodextrin (b-CD) and (2-hydroxypropyl)-b-cyclodextrin (HP-b-CD) in aqueous solutions (pH 7.4 and 5). The CE analysis of the solutions exposed to UV-A and UV-B radiations showed a photoprotective effect by b-CD; conversely, HP-b-CD proved to favor the drug photodegradation. Moreover, evidences for CDs-mediated stereoselective photodegradation of rac-nicardipine were obtained. In fact, two distinct photodegradation profiles were observed for the nicardipine enantiomers in the presence of the CDs. The photodegradation was found to follow an apparent first-order kinetics and two different kinetic constants (k) were obtained for the two enantiomers. After exposure to UV-A and UV-B radiations, the solutions contained residual nicardipine with a significant change in the enantiomeric ratio; this effect was depending on the CD used for the inclusion complexation.