Purification and mass spectrometry study of Maillard reaction impurities in five acyclic nucleoside antiviral drugs.

Maillard degradation products may lead to a decrease in active pharmaceutical ingredients and an increase in harmful substances. In this study, five acyclic nucleoside antiviral drugs (adefovir dipivoxil, famciclovir, tenofovir dipivoxil, acyclovir, and ganciclovir) were studied. Compatibility of APIs and lactose was performed, and the Maillard reaction products were monitored by HPLC-photodiode array detection and UHPLC-ESI-MS. Eight Maillard reaction products were detected, of which six were found to be new stable compounds (impurities 1-6) and were purified and identified by NMR spectroscopy. Moreover, the six new impurities were analyzed by MS/MS, and their mass spectrometric fragmentation mechanisms were proposed. The loss of a neutral fragment at 282 Da by the fragmentation of the lactose moiety was observed in the tandem mass spectra of all the impurities. This is the first systematic study of the Maillard reaction in the case of acyclic nucleosides antiviral drugs, and it has achieved good results. The results will be helpful for understanding the mass spectrometric fragmentation mechanisms of Maillard reaction products and the stability of acyclic nucleosides, and will provide suggestions for maintaining the stability and optimizing the storage and transportation conditions of these drugs.