Isolation and Identification of New Sildenafil Analogues from Dietary Supplements

Three derivatized thio-sildenafil compounds were isolated from herbal health supplements. The structures of these three compounds were determined by NMR, high resolution MS, LC/MS/MS, UV and IR spectroscopy. Compound 1 and 2 have been identified as propoxyphenyl thioaildenafil and propoxyphenyl aildenafil, respectively. Compound 3, named propoxyphenyl hydroxyethylthiosildenafil, is an analogue of thiosildenafil. The major difference between compound 3 and thiosildenafil is that propoxy and hydroxyethyl groups in compound 3 replaced the function groups of ethoxyl and methyl in thiosildenafil. Since their structures were similar to that of sildenafil or thiosildenafil, according to structure-activity relationship, the side effects of these analogues might be also associated with that of sildenafil or thio-sildenafil. Based on this study, these three analogues have been included in the inspection list of illegal adulterants in TFDA.