Determination of phosphodiesterase-5 inhibitors and analogs using high-performance liquid chromatography with ultraviolet detection.

A considerable number of erectile dysfunction products, and dietary supplements suspected of containing phosphodiesterase-5 (PDE-5) inhibitors, have been analyzed by the US Food and Drug Administration. Often these samples are found to contain the approved active pharmaceutical ingredients (APIs) such as sildenafil, tadalafil or vardenafil. However, analogs of these APIs have also been identified in many samples and products containing multiple PDE-5 inhibitors have also been found.

Cyanide and amygdalin as indicators of the presence of bitter almonds in imported raw almonds.

Consumer complaints received by the U.S. Food and Drug Administration in August 2010 about raw organic almonds tasting "bitter" opened an investigation into the presence of bitter almonds in the imported product.

Isolation and structural characterization of two tadalafil analogs found in dietary supplements.

During routine screenings of two "libido enhancer" dietary supplements using LC-MS(n), two compounds were detected that displayed structural similarities to tadalafil. These compounds were isolated from the supplements using high-performance liquid chromatography with fraction collection, and were characterized further using accurate mass determination and NMR. "Compound 1" had an m/z of 434 for the [M+H]⁺ ion, with a corresponding chemical formula of C₂₄H₂₄N₃O₅.

Structural characterization of sulfoaildenafil, an analog of sildenafil.

Phosphodiesterase type 5 (PDE-5) inhibitors represent a class of drugs used primarily in the treatment of erectile dysfunction. Currently, three PDE-5 inhibitors have been approved by the U.S.

Analysis of undeclared synthetic phosphodiesterase-5 inhibitors in dietary supplements and herbal matrices by LC-ESI-MS and LC-UV.

A liquid chromatography-electrospray ionisation-mass spectrometry (LC-ESI-MS) method was developed to screen for the presence of synthetic phosphodiesterase type 5 (PDE-5) inhibitors including sildenafil, tadalafil and vardenafil. The method was applied to the analysis of dietary supplements and bulk herbal materials. Bulk powders or composites of tablets, capsules or liquids were prepared and an extraction of PDE-5 inhibitors was performed using a mixture of acetonitrile and water with sonication.

Analysis of antibiotics by capillary electrophoresis.

Recent developments in the characterization of antibiotics are reviewed. Many capillary electrophoretic techniques have been utilized in their analyses, addressing various aspects of quantifying, profiling, and monitoring. Laser-induced fluorescence detection systems demonstrated their usefulness in clinical settings and in the monitoring of residue levels in food matrices.