Pyrazolopyrimidines in ‘all-natural’ products for erectile dysfunction treatment: the unreliable quality of dietary supplements

<div><p>A herbal food supplement advertised as a potency pill was screened for the presence of PDE5 inhibitors. The resulting signals were characterised by UV, LC-MS in ESI-negative mode, and NMR spectroscopy using 1D and 2D experiments. Several substances were identified, bearing the basic chemical structure of sildenafil, but were not supposed to exhibit PDE5 inhibition. These compounds may be process-related impurities or by-products of different reaction steps in the synthesis of PDE5 analogues. As they were found to be present in different capsules at different concentrations, this is an example of the unreliable quality of dietary supplements.</p></div

Isotopologue Profiling of Triterpene Formation under Physiological Conditions. Biosynthesis of Lupeol-3-(3′‑<i>R</i>‑hydroxy)-stearate in <i>Pentalinon andrieuxii</i>

The biosynthesis of lupeol-3-(3′<i>R</i>-hydroxy)-stearate (procrim b, <b>1</b>) was investigated in the Mexican medicinal plant <i>Pentalinon andrieuxii</i> by ¹³CO₂ pulse-chase experiments. NMR analyses revealed positional enrichments of ¹³C₂-isotopologues in both the triterpenoid and the hydroxystearate moieties of <b>1</b>. Five of the six isoprene units reflected a pattern with [1,2-¹³C₂]- and [3,5-¹³C₂]-isotopologues from the respective C₅-precursors, IPP and DMAPP, whereas one isoprene unit in the ring E of <b>1</b> showed only the [3,5-¹³C₂]-connectivity of the original C₅-precursor, due to rearrangement of the dammarenyl cation intermediate during the cyclization process. The presence of ¹³C₂-isotopologues was indicative of [¹³C₂]­acetyl-CoA being the precursor units in the formation of the fatty acid moiety and of the triterpene via the mevalonate route. The observed labeling pattern was in agreement with a chair-chair-chair-boat conformation of the (<i>S</i>)-2,3-oxidosqualene precursor during the cyclization process, suggesting that the lupeol synthase from <i>P. andrieuxii</i> is of the same type as that from <i>Olea europea</i> and <i>Taraxacum officinale</i>, but different from that of <i>Arabidopsis thaliana</i>. The study shows that ¹³CO₂ pulse-chase experiments are powerful in elucidating, under <i>in vivo</i> conditions and in a single experiment, the biosynthesis of complex plant products including higher terpenes