Characterization of Sildenafil 1 analogues by MS/MS and NMR: a guidance for detection and structure elucidation of novel phosphodiesterase-5 inhibitors.

Novel synthetic analogues of Sildenafil are constantly detected as adulterants in counterfeit drugs and dietary supplements. Their intake constitutes a serious health hazard as side effects are unknown. In this paper an investigation is carried out on NMR and MS/MS spectra of Sildenafil, Thiosildenafil, Acetildenafil and thirteen of their analogues: A list of key signals is reported and discussed with the intent to provide a tool that can help in detecting adulteration and in elucidating the structure of novel analogues. In this view extensive spectral data were reported, discussed and summarized in tables. A discussion on mass fragmentation and magnetic resonance features is also provided to rationalize assignation. Moreover, comprehensive information on the route of synthesis is provided for the benefit of those medicines control laboratories that need to synthesize analogues reference standards in house.