SIMULTANEOUS DETERMINATION OF EIGHT PDE5-IS POTENTIALLY ADULTERATED IN HERBAL DIETARY SUPPLEMENTS WITH TLC AND HPLC-PDA-MS METHODS

A set of simple TLC and HPLC-PDA-MS methods were developed for detection of counterfeit herbal dietary supplements by the qualitative and quantitative analysis of eight phosphodiesterase type 5 inhibitors (PDE5-Is), sildenafil, hongdenafil, homosildenafil, hydroxyhomosildenafil, vardenafil, pseudovardenafil, tadalafil, and aminotadalafil. The analytical approach is simple for rapid screening with TLC and reliable with HPLC-PDA-MS. Good linearity (r20.999 over the concentration range of 8.1 to 211.2g/ml), sensitivity (limits of quantification 0.04-0.09g/ml), accuracy (97.03-101.25%), and precision (RSD (%)1.32%) were achieved for all analytes. The methods were applied for detection of 36 commercial herbal dietary supplements suspected containing PDE5-Is. In addition, the characteristic MS fragmentations of three main typical structures, sildenafil, vardenafil, and tadalafil, were discussed and summarized, which are very helpful in rapid screening identification and determination of suspected chemicals not claimed in herbal products. Results have demonstrated that established TLC and HPLC-PDA-MS methods are good confirmation and quantification test schemes for the eight target compounds.