Isolation and identification of a novel vardenafil analogue, propoxy-vardenafil, found as an adulterant in a health supplement

Background: A novel vardenafil analogue was detected from a health wine claimed to be anti-impotence during a special inspection in an online store.

Methods: The unknown compound was found by using ultra-high performance liquid chromatography coupled to quadrupole time of flight mass spectrometry (UHPLC/Q-TOF MS). The characteristic product ions were similar to those of vardenafil. The UV spectrum of the compound closely mirrored that of vardenafil. The analogue underwent purification by semi-preparative HPLC and structurally identified by FT-IR and NMR analysis.

Results: Based on the data, The structure of the analogue was characterized as 2-[2-propyloxy-5-(4-ethylpiperazin-1-yl)sulfonylphenyl]-5-methyl-7-propyl-3H-imidazo [5,15,1-f] [1,2,4]triazin-4-one, simplified as propoxy-vardenafil.

Conclusion: To the best of our knowledge, the analogue has not been reported and is even only ninth vardenafil analogue, which was confirmed that a n-propyloxy group had replaced the ethoxy group on the aromatic ring of vardenafil. Therefore, It is essential to pay more attention to vardenafil analogues in the routine inspection of health supplements.