A screen for known PDE-5 inhibitors in a dietary supplement product marketed for “enhanced sexual performance” detected a compound that structurally resembled tadalafil. The compound was isolated from the supplement matrix using high-performance liquid chromatography with ultraviolet detection (HPLC-UV) and a fraction collector, and was further characterized using nuclear magnetic resonance (NMR), liquid chromatography–mass spectrometry (LC–MS), as well as high-resolution accurate mass mass spectrometry (HRAM-MS). The analog had an accurate mass of m/z 420.15614 (error is 1.77235ppm) for the protonated species [M+H] + , corresponding to a molecular formula of C 23 H 22 N 3 O 5 . Mass spectral fragmentation data suggested that the modification occurred in place of the CH 3 located on the pyrazinopyridoindole-1,4-dione of tadalafil. NMR was utilized to further elucidate the configuration of the substitution. The analysis indicated that the moiety is a CH 2 CH 2 OH, hydroxyethyl group. The new analog has been named 2-hydroxyethylnortadalafil.