German researchers have analyzed herbal supplements being marketed to men as potency pills to boost sexual performance. They used nuclear magnetic resonance and chromatography-coupled mass spectrometry to identify suspected, unapproved phosphodiesterase-5 inhibitors related to sildenafil, vardenafil, and tadalafil, drugs used for erectile dysfunction.

The analysis identified analogs of Pfizer’s sildenafil in which the piperazine ring and the sulfonyl group were replaced with a piperazinone and a hydroxyethyl moiety, respectively. These compounds may lead to an increased risk of heart failure.

• Identification of novel sildenafil-analogues in an adulterated herbal food supplement
  U. Wollein, W. Eisenreich, N. Schramek,
  J. Pharm. Biomed. Anal. 2011.
  DOI: 10.1016/j.jpba.2011.07.012