Analytical strategies for identifying PDE5 inhibitors in damiana (Turnera diffusa) products

The growing use of herbal supplements marketed for sexual enhancement has raised concerns regarding their adulteration with pharmaceutical compounds, particularly phosphodiesterase type 5 inhibitors (PDE5i). Damiana (Turnera diffusa) is commonly included in such supplements due to its traditional aphrodisiac properties. This study presents the development and validation of three analytical methods (LC-DAD, LC-Q MS, and FIA-ToF MS) for the sensitive detection and accurate quantitation of four PDE5i (avanafil, vardenafil, sildenafil, and tadalafil) in damiana-based food supplements. Method performance was assessed and compared using validation parameters such as sensitivity, specificity, accuracy, and precision. Although all three methodologies demonstrated very good analytical performance, the FIA-ToF MS approach offered a clear advantage by reducing the analysis time to just 1 min per sample, compared with 26 min required for the chromatographic methods. This work presents the first validated FIA-ToF MS screening workflow specifically developed for the detection and quantitation of PDE5 inhibitors in damiana-based products. The method combined high-throughput analysis with satisfactory sensitivity, precision and accuracy, and was successfully applied to samples intentionally adulterated at LOQ-level concentrations. None of the four PDE5i were detected in the 20 damiana supplements analyzed. Nevertheless, this methodology offers a rapid and reliable screening tool for the routine analysis of these commercial products in quality control and regulatory laboratories, contributing to adulteration detection, consumer safety and regulatory enforcement.