Investigation of the Presence of Sildenafil in Herbal Dietary Supplements by Validated HPLC Method

Innovative utilization of silver nanoparticles localized surface plasmon resonance for green and sensitive spectrofluorimetric analysis of sildenafil and xipamide in pure forms and pharmaceutical preparations

A green, novel, simple and sensitive spectrofluorimetric approach was investigated and validated for the analysis of two important cardiovascular drugs namely; sildenafil citrate and xipamide using silver nanoparticles as a fluorescence probe (Ag-NPs). Silver nanoparticles were prepared through chemical reduction of silver nitrate using sodium borohydride in distilled water without using non-green organic stabilizer. These nanoparticles were stable, water soluble and had high fluorescence. After addition of the studied drugs, noticeable quenching of Ag-NPs fluorescence occurred. The intensity of Ag-NPs fluorescence was measured at 484 nm (λex 242 nm) before and after complex formation with these studied drugs. The difference between these values (ΔF) were linear with the concentrations in the following ranges (1.0-10.0 μg/mL), (0.5-5.0 μg/mL) for sildenafil and xipamide, respectively. The formed complexes did not need to be separated by solvent extraction before measurement. For proving the complex formation between the two studied drugs and silver nanoparticles, stern volmer method was applied. The suggested method was perfectly validated in compliance with the international conference on harmonization (ICH) Guidelines and the outcomes were acceptable. Furthermore, suggested technique was perfectly applied for the assay of each drug in its pharmaceutical dosage form. Eventually assessment of method greenness was performed using different tools and found that the suggested method was safe and eco-friendly.

Determination of Phosphodiesterase Type-5 Inhibitors (PDE-5) in Dietary Supplements

This study proposed a high-performance thin-layer chromatography (HPTLC) screening method to detect phosphodiesterase 5 (PDE-5) inhibitors as possible adulterant agents in various dietary supplements. Chromatographic analysis was performed on silica gel 60F254 plates using a mixture of ethyl acetate:toluene:methanol:ammonia in a volume ratio of 50:30:20:0.5 as a mobile phase. The system provided compact spots and symmetrical peaks of sildenafil and tadalafil with retardation factor values of 0.55 and 0.90, respectively. The analysis of products purchased from the internet or specialized stores demonstrated the presence of sildenafil, tadalafil, or both compounds in 73.3% of products, highlighting inadequacies and inconsistencies in the labeling, as all dietary supplements were declared to be natural. The results were confirmed using ultra-high-performance liquid chromatography coupled with a positive electrospray ionization high-resolution tandem mass spectrometry (UHPLC-HRMS-MS) method. Furthermore, in some samples, vardenafil and various analogs of PDE-5 inhibitors were detected using a non-target HRMS-MS approach. The results of the quantitative analysis revealed similar findings between the two methods, with adulterant quantities found to be similar to or higher than those in approved medicinal products. This study demonstrated that the HPTLC method is a suitable and economical method for screening PDE-5 inhibitors as adulterants in dietary supplements intended for sexual activity enhancement.

Spider diagram and sustainability evaluation of UV-methods strategy for quantification of aspirin and sildenafil citrate in the presence of salicylic acid in their bulk and formulation

The cutting-edge combination of aspirin (ASA) and sildenafil citrate (SIC) has been presented as a suggested dosage form for the treatment of thin endometrium and erectile dysfunction, particularly in patients with cardiovascular diseases. However, ASA is highly sensitive to degradation into its major deterioration product, known as salicylic acid (SA). Consequently, it is eminently essential to evolve approaches for the synchronous quantification of ASA and SIC in the presence of SA. The main objective of this work is to develop three approaches for the synchronous quantification of ASA and SIC in the presence of SA in their commixtures and suggested formulations without any prior separation. Three green UV-methods were employed for the synchronous quantification, namely: Dual Wavelength in Ratio Spectra (DW-RS), Advanced Amplitude Centering (AAC), and Double Divisor of Ratio Difference Derivative (DDRD-D₁). In DW-RS and AAC two-wavelength manipulation was used for resolution, while in DDRD-D₁ only an appropriate wavelength for the synchronous quantification of the triplex commixture was used. All approaches can be able to resolve the highly interfering spectrum of the three components presented in the triplex commixture. Good linearity was inspected in the range of 20.0-100.0, 5.0-50.0, and 4.0-60.0 μg/mL for the ASA, SIC, and SA, respectively. All developed approaches have been advocated in accordance with ICH guidelines. All results from these approaches are presented and statistically reconciled with the proclaimed HPLC method, with no considerable differences. Furthermore, the approaches' eco-friendliness was predestined by Analytical Greenness (AGREE), and the complex GAPI. Moreover, the sustainability of the used solvent was evaluated by Green Solvents Selecting Tool (GSST); in addition, the greenness of the solvent was evaluated by Greenness Index tool with a spider diagram. The suggested UV-methods may be employed for routine quality control studies of the suggested formulations ASA & SIC since they were considered sustainable, economical, and effective.

DoE Screening and Optimization of Liquid Chromatographic Determination of Nicotinic Acid and Six Statins: Application to Pharmaceutical Preparations and Counterfeit Detection

An isocratic reversed-phase high performance liquid chromatographic method has been developed and validated to simultaneously determine nicotinic acid, pravastatin sodium, rosuvastatin calcium, atorvastatin calcium, pitavastatin calcium, lovastatin sodium and simvastatin sodium in focus on counterfeit drug detection. Thin-layer chromatography, nuclear magnetic resonance and mass spectrometry have been additionally performed to verify the identification of adulterants of counterfeit herbal medicines. Chromatographic separation was carried out on Inertsil® ODS-3 C18 (4.6 × 150 mm, 5 μm) with isocratic mobile phase elution containing a mixture of acetonitrile: methanol: 25 mM potassium dihydrogen phosphate buffer, pH 2.86 adjusted with 0.1 M o-phosphoric acid (48: 30: 22, v/v/v), at a flow rate of 1 mL/min and with UV detection at 238 nm. The design of experiment methodology, Plackett-Burman and Box-Behnken designs, was used to screen and optimize the mobile phase composition. The validation of the method was also carried out under the International Conference on Harmonization guidelines. The developed method was sensitive, accurate, simple, economical and highly robust, in addition to the comprehensiveness and novelty of this method for separating the seven drugs. The results were statistically compared with the reference methods used Student's t-test and variance ratio F-test at P < 0.05.

Analysis of Aspirin, Prasugrel and Clopidogrel in Counterfeit Pharmaceutical and Herbal Products: Plackett–Burman Screening and Box–Behnken Optimization

An isocratic reversed-phase high-performance liquid chromatographic method has been developed and validated for the simultaneous determination of aspirin, prasugrel HCl and clopidogrel bisulfate in the presence of clopidogrel-related compound (impurity-A) in focus on counterfeit. This method was used to determine counterfeited antiplatelet drugs in two substandard Indian pharmaceutical products sold on the market in Yemen and two traditional herbal medicines sold on the market in China. Thin layer chromatography and mass spectrometry of counterfeit herbal medicines have additionally been carried out to verify the identification of adulterants. Chromatographic separation was performed on Inertsil ® ODS-3 C18 (4.6 × 250 mm, 5 μm) with isocratic mobile phase elution containing a mixture of acetonitrile: (25 mM) potassium dihydrogen phosphate buffer, pH 2.7 adjusted with 0.1 M o-phosphoric acid (79: 21, v/v), at a flow rate of 1 mL/min and UV detection at 220 nm. Designs of experiment methodology, Plackett–Burman and Box–Behnken designs were used for the screening and optimization of the mobile phase composition. The method validation was also performed in accordance with the International Council on Harmonization (ICH) guidelines. The method developed for routine analysis was found to be sensitive, simple, accurate and highly robust. The results were statistically compared to reference methods using Student’s t-test and variance ratio F-test at P &lt; 0.05.