Counterfeiting honey with phosphodiesterase inhibitors for sexual activity enhancement: detection using high-performance liquid chromatography coupled with a photodiode array detector (HPLC-PAD)

Abstract

Globally, there have been several reports of natural products contaminated with illegal adulterants that threaten consumer health because of their adverse pharmacological effects. To treat erectile dysfunction in men, herbal medicine is often adulterated with synthetic phosphodiesterase type 5 (PDE-5) inhibitors. Honey, which is popularly used for its health benefits, is subjected to adulteration with PDE-5 inhibitors. In this study, a rapid and reliable analytical method was proposed to determine the level of adulteration in honey samples. A total of 18 honey samples were tested for the presence of PDE-5 inhibitors (sildenafil, tadalafil and vardenafil) using a high-performance liquid chromatographic method coupled with a photodiode array detector (HPLC-PAD). Chromatography was performed using the Agilent ZORBAX SB-C18 column, with acetonitrile and buffer in the ratio of 1:4 as the mobile phase. Sildenafil, tadalafil and vardenafil reference standards were used for calibration. The retention times of the standards were 21.67, 18.15 and 21.30 min respectively. Of the total samples tested, 55% were positive for PDE-5 inhibitors. Six samples contained sildenafil, three samples contained tadalafil and one sample contained vardenafil. The findings from this study demonstrate that the HPLC-PAD method is suitable and economical for screening PDE-5 inhibitors as adulterants in honey samples marketed for use as sexual activity enhancers. Regular inspections of adulterated products are thus warranted to ensure the safety and health of consumers.