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 C(24)H(24)N(3)O(5). Compound 2 had an m/z of 432 for the [M+H](+) ion, with a corresponding chemical formula of C(25)H(26)N(3)O(4). Although mass spectrometry indicated that these modifications occurred in place of the -CH(3) found on the pyrazinopyridoindole-1,4-dione of tadalafil, NMR was required to elucidate the correct configurations of these substitutions. The data obtained using NMR indicated that the structure of the -C(3)H(7)O moiety found in Compound 1 was 2-hydroxypropyl, and the -C(4)H(9) in Compound 2 was n-butyl. These new analogs were given the names 2-hydroxypropylnortadalafil and n-butylnortadalafil, respectively. Published by Elsevier B.V.