Abstract
A feasible and cost effective reverse-phase high-performance thin layer chromatography (RP-HPTLC) based method was developed for the quantification of sildenafil (SLD) using eco-friendly EtOH:H2O (9.5:0.5 v/v) as mobile phase. SLD was subjected to stress conditions according to the International Conference on Harmonization (ICH) guidelines. The drug undergoes significant structural changes under oxidative stress condition to the N-oxide derivative. The oxidation product Sildenafil N-oxide (SDL N-oxide) designated in the European Pharmacopeia (EP) as impurity B was characterized utilizing 1D- and 2D-NMR as well as High Resolution Electrospray Ionization Mass Spectroscopy. The aphrodisiac potency of SDL N-oxide in comparison with SLD was evaluated in vivo using rats as experimental animal model. The evaluation based on the following parameters: mount, intromission and ejaculation latencies (ML, IL and EL, respectively), mounting and intromission frequencies (MF and IF, respectively), and postejaculatory interval (PEI). SLD N-oxide expressed similar aphrodisiac effect to SLD but with less potency. Molecular docking of SDL N-oxide along with the parent drug SLD, indicated a strong binding affinity and similar binding pattern within the active site of phosphodiesterase 5 (PDE5). However, the docking score of SLD N-oxide was slightly lower as compared to SLD in agreement with the biological study findings.
Highlights
In 1989, sildenafil (SLD) was primarily investigated as medication for the treatment of angina pectoris and hypertension
An eco-friendly HPTLC method was developed for the quantification of SLD
The proposed mobile phase composed of the green solvent mixture EtOH: H2O (9.5:0.5 v/v) produced sharp, symmetrical and well resolved peak at Rf value of 0. 23 (Fig. 2) for SLD standard after saturation for 30 min
Summary
In 1989, sildenafil (SLD) was primarily investigated as medication for the treatment of angina pectoris and hypertension. HPLTC utilizing a relatively very small quantity of the mobile phase This makes HPTLC the most time and cost-effective method of chromatographic a nalysis[9,10]. HPTLC is feasible for the development of chromatographic fingerprint to determine and identify complex herbal extracts just like HPLC and GC. Two HPTLC methods utilizing normal phase silica gel plates were developed for the quantification and detection SLD in tablets and herbal formulations adulterated with the d rug[13,14]. Another HPTLC method was designed for the simultaneous quantification of marketed table formulation containing SLD and dapoxetine[15]. Analytical techniques associated with “green analytical chemistry or environmentally-benign analytical techniques” have been increased significantly in literature[18,19]
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