DETECTION AND QUANTIFICATION OF SILDENAFIL AND TADALAFIL AS ADULTERANTS IN COMMERCIAL HERBAL SUPPLEMENTS USING HPLC

Abstract

A simple, rapid and accurate reversed-phase high performance liquid chromatographic (RP-HPLC) method was developed and validated for the simultaneous determination of sildenafil and tadalafil in twenty herbal dietary supplements sold for enhancing sexual performance in Malaysia. Chromatographic separation was achieved with a Hypersil Gold C18 column (150 mm × 4.6 mm i.d., 5 µm particle size) at 30 °C, using a mobile phase consisting of 20 mM of ammonium acetate (adjusted to pH 5.5 with orthophosphoric acid) and acetonitrile at a flow rate of 1.0 mL/min. The UV detection wavelength was set at 245 nm. Tadalafil and sildenafil eluted out from the column at retention times 5.8 min and 6.3 min, respectively. The method was validated in accordance to specificity, accuracy, linearity and range, precision, limit of detection (LOD) and limit of quantification (LOQ). Calibration curves were linear over the concentration range of 10−30 µg/mL and 1−3 µg/mL for sildenafil and tadalafil, respectively. The LOD values of sildenafil and tadalafil were 1.00 µg/mL and 0.07 µg/mL, respectively while LOQ values were 3.02 µg/mL and 0.21 µg/mL, respectively. The recoveries of both compounds were in the range of 99.11−100.87%. The RSD of repeatability and intermediate precision were less than 2%. The proposed method was successfully applied in the screening and quantification of tadalafil and sildenafil in adulterated herbal dietary samples.

Keywords: Herbal dietary supplements; Sildenafil; Tadalafil; HPLC; Adulteration.