Structure elucidation of sildenafil analogues in herbal products.

The structure of unknown compounds present in herbal products was elucidated using liquid chromatography-electrospray ionization-mass spectrometry, direct-infusion electrospray ionization-mass spectrometry, and nuclear magnetic resonance. Compounds 1-3 were identified as sildenafil analogues, 1 bearing an N-ethylpiperazine moiety instead of an N-methylpiperazine, and an acetyl group instead of the sulfonyl group, named acetildenafil, 2 bearing an N-ethylpiperazine moiety instead of an N-methylpiperazine (homosildenafil), and 3 bearing an N-hydroxylethylpiperazine moiety instead of an N-methylpiperazine, named hydroxyhomosildenafil. When analysing products marketed for penile erectile dysfunction or marketed as aphrodisiacs, attention should be given to the possible presence of these components.

Analysis of optically active compounds using conventional chromatography with a circular dichroism detector.

Analysis of optically active compounds in complex samples is often based on chiral chromatography or capillary electrophoresis in order to separate the enantiomers. This requires a chiral reagent, when using conventional chromatography, or an expensive chiral column, or a chiral selector, when using capillary electrophoresis. The type of column, reagent, or additive depends highly on the compound to be analysed. A simple and generally applicable method is using a conventional HPLC column coupled to a CD detector. Separation of enantiomers is not required, as they can be identified by a positive or negative peak. A racemate does not produce a peak; neither does an optically inactive compound. The application of HPLC-CD for the identification of pharmacologically active compounds, such as dexamphetamine, 5-hydroxytryptophan, (-)-huperzine A, and interferon, as standards, in registered drugs, in falsifications, and in food supplements is described.