Photostability of drugs: photodegradation of melatonin and its determination in commercial formulations

The photostability of melatonin, a hormone used as supplementary drug in th e alleviation of jet-lag and other sleep disorders, was studied. The drug p hotodegradation at different pH values was monitored by HPLC methods. The m ain photoproduct was isolated and characterised on the basis of the NMR, FT IR, and mass spectra. A HPLC method, in combination with a post-column on-l ine photochemical derivatisation was developed for the selective and reliab le quality control of commercially available melatonin containing products. (C) 2000 Elsevier Science B.V. All rights reserved.