Identification of a novel sildenafil analogue in an adulterated herbal supplement.

iErect, a new dietary supplement marketed as "100% natural" and sold over the Internet, was analyzed. It contains thiosildenafil, a sildenafil analogue already reported as an adulterant in herbal formulations, and a new compound whose structure was elucidated after isolation using NMR, MS and IR. It was named depiperazinothiosildenafil as it results from the hydrolytic cleavage of the S-N bond of the sulfonamide group of thiosildenafil. A capsule of iErect contains a very high amount (≈220mg) of thiosildenafil and ≈30mg of depiperazinothiosildenafil, which places consumers at risk for potentially serious side-effects.