Identification of a Tadalafil Analogue Adulterated in a Dietary Supplement

A dietary supplement which was claimed on the treatment of male erectile dysfunction was firstly screened by TLC, and two suspected spots showed on the TLC plate tinder the detection of UV 254 nm. One of the spot (1) was determined as tadalafil by direct comparison of its TLC, UV, and LC/MS/MS data with the reference standard of tadalafil. The other suspected spot was identified by extraction, separation and purification from the sample to get a yellowish powder (compound 2). The structure of compound 2 with an amino group instead of the N2-methyl group in the piperazinedione ring of tadalafil was determined to be (6R,12aR)-2-amino-6-(1,3-benzodioxol-5-yl)-2,3,6,7,12,12a-hexahydro-pyrazino[1',2':1,6]pyrido[3,4-b]indole-1,4-dione by NMR, circular dichroism, and mass spectroscopy and compound 2 was named as aminotadalafil which was first detected in our laboratory. These two compounds were illegally adulterated into the dietary supplement and compound 2 has been listed as a new item for the screening of aphrodisiac adulterants.