Isolation and structural characterisation of a propoxyphenyl-linked thiohomosildenafil analogue found in a herbal product

Abstract

A propoxyphenyl-linked thiohomosildenafil analogue, one of the sildenafil analogues, was found in an herbal product. It was isolated by semi-preparative high-performance liquid chromatography (HPLC). The structure was established based on a comparison of chromatographic and spectroscopic behaviour with other sildenafil analogues using HPLC with diode array detection, quadrupole time-of-flight mass spectrometry (Q-TOF/MS), and nuclear magnetic resonance (NMR) spectroscopy. The HPLC analysis showed separation from known sildenafil analogues with a similar chromatographic retention time. An [M + H]⁺ ion at m/z 519.22 was detected by mass spectrometry corresponding to an empirical formula of C₂₄H₃₄N₆O₃S₂. The structure was similar to that of thiohomosildenafil, except that the ethoxy group attached to the phenyl ring was substituted for a propoxy group. It was assigned as 5-[2-propoxy-5-(4-ethylpiperazin-4-ylsulfonyl)phenyl]-3-methyl-1-n-propyl-4,5,dihydro-1H-pyrazole[7,1,d]pyrimidin-4-thione and named as propoxyphenyl-thiohomosildenafil because the structure was considerably similar to thiohomosildenafil.

Keywords:

• propoxyphenyl-thiohomosildenafil
• sildenafil analogue
• UV
• Q-TOF/MS
• NMR

Acknowledgements

This study was supported by a grant from the Criminal Investigations Office of the Korea Food & Drug Administration (KFDA) in 2012.