Analysis of herbal dietary supplements for sexual performance enhancement: first characterization of propoxyphenyl-thiohydroxyhomosildenafil and identification of sildenafil, thiosildenafil, phentolamine and tetrahydropalmatine as adulterants - Balayssac, S; Gilard, V; Zedde, C; Martino, R; Malet-Martino, M (J Pharm Biomed Anal, 2012)