Development of a specific fragment pattern-based quadrupole-Orbitrap mass spectrometry method to screen adulterated products of phosphodiesterase-5 inhibitors and their analogues

Isolation and characterization of a novel tadalafil analogue adulterant, N-cyclohexyl nortadalafil, in a dietary supplement

A novel tadalafil analogue was detected during routine screening of dietary supplements suspected to be adulterated with an erectile dysfunction drug(s) by using ultra-high-performance liquid chromatography coupled to Quadrupole-Exactive Orbitrap mass spectrometry (UPLC‑Q‑Exactive Orbitrap/MS). The MS² spectrum of the compound was highly similar to that of tadalafil within the range of < 300 m/z. The UV spectrum of the compound was almost identical to that of tadalafil. The analogue was purified by semi-preparative HPLC and structurally elucidated by FT-IR, MS and NMR analysis. The analogue was finally determined as N-cyclohexyl nortadalafil, featuring the cyclohexyl group instead of the N-methyl group on the piperazinedione ring of tadalafil.

Detection of 94 PDE-5is and Their Analogs Including N-Desmethylthiosildenafil in Various Formulations of Dietary Supplements and Food Samples Using HPLC and LC-Q-TOF/MS

Consumption of foods and dietary supplements (DS) adulterated with unprescribed or non-permitted phosphodiesterase-5 inhibitors (PDE-5i) and their analogs can cause serious risk to human health. This study aims to analyze 93 PDE-5i and their analogs present in adulterated foods and DS using an established and validated method involving high-performance liquid chromatography (HPLC). The method was validated in solid and liquid samples, resulting in a limit of detection and quantitation of 0.03-0.5 and 0.08-1.6 μg/mL, respectively. Using the validated method, a total of 404 samples were screened. It was found that 32% of 404 samples were illegally adulterated with PDE-5i and their analogs; moreover, 16.9% of the adulterated samples were found to contain more than three compounds. HPLC-quadrupole-time-of-flight (TOF)/mass spectrometry (MS) analysis was conducted on all the samples to confirm the detected compounds accurately based on fragmentation ion patterns. In addition, sildenafil and tadalafil were detected from the capsule shells of DS unusually. Subsequently, the detected compounds were identified and quantified using HPLC at concentrations ranging from 0.007 to 370.0 mg/g. NMR analysis was carried out to confirm the accurate chemical structure of a compound found during the TOF/MS analysis, which did not match with the 93 reference standards.; it was identified to be N-desmethylthiosildenafil. In this study, various PDE-5i compounds and their analogs were detected from low to high concentrations in a sample. Therefore, the study sheds light on the misuse of PDE-5i and their analogs in consumable products, which pose a severe threat to public health.

Lodenafil

Lodenafil is a class of drugs called an inhibitor of PDE5 which also include a wide range of other erectile medicines, such as sildenafil, tadalafil and vardenafil. It is part of a new generation of PDE5 inhibitors that includes udenafil and avanafil. Lodenafil is a prodrug manufactured in the form of lodenafil carbonate, the carbonate dimer that divides in the body into two active drug lodenafil molecules. The oral bioavailability of this formulation is higher than that of the parent drug. This article discusses, by a critical comprehensive review of the literature on lodenafil in terms of its description, names, formulae, elemental composition, appearance, and therapeutic uses. The article also discusses the methods for preparation of lodenafil, its physical-chemical properties, analytical methods for its determination, pharmacological-toxicological properties, and dosing information.

Facing Counterfeit Medications in Sexual Medicine. A Systematic Scoping Review on Social Strategies and Technological Solutions

Introduction

The counterfeit phenomenon is a largely under-reported issue, with potentially large burden for healthcare. The market for counterfeit drugs used in sexual medicine, most notably type 5 phosphodiesterase inhibitors (PDE5i), is rapidly growing.

Aims

To report the health risks associated with the use of counterfeit medications, the reasons driving their use, and the strategies enacted to contain this phenomenon.

Methods

A systematic scoping review of the literature regarding counterfeit PDE5i was carried between January and June 2021, then updated in August 2021.

Main Outcome Measure

We primarily aimed to clarify the main drivers for counterfeit PDE5i use, the health risks associated, and the currently available strategies to fight counterfeiters.

Results

One hundred thirty-one records were considered for the present scoping review. Production of fake PDE5i is highly lucrative and the lacking awareness of the potential health risks makes it a largely exploitable market by counterfeiters. Adulteration with other drugs, microbial contamination and unreliable dosages make counterfeit medications a cause of worry also outside of the sexual medicine scope. Several laboratory techniques have been devised to identify and quantify the presence of other compounds in counterfeit medications. Strategies aimed at improving awareness, providing antitampering packaging and producing non-falsifiable products, such as the orodispersible formulations, are also described.

Clinical implications

Improving our understanding of the PDE5i counterfeit phenomenon can be helpful to promote awareness of this issue and to improve patient care.

Strengths & Limitations

Despite the systematic approach, few clinical studies were retrieved, and data concerning the prevalence of counterfeit PDE5i use is not available on a global scale.

Conclusion

The counterfeit phenomenon is a steadily growing issue, with PDE5i being the most counterfeited medication with potentially large harmful effects on unaware consumers.

Sansone A, Cuzin B, and Jannini EA. Facing Counterfeit Medications in Sexual Medicine. A Systematic Scoping Review on Social Strategies and Technological Solutions. Sex Med 2021;9:100437.

Screening and elucidation of fragmentations of 23 diuretics in dietary supplements using UHPLC-Q-Orbitrap

Diuretics are used to treat the edematous state in cases of renal insufficiency, nephrotic syndrome, liver cirrhosis, and heart failure. These compounds are used by athletes to lose weight and are included in the list of prohibited substances by the World Anti-Doping Agency. They are also used by obese and overweight people for losing weight, and there are a number of recent reports on the contamination of dietary supplements with diuretics. Due to the alluring online marketing and blogging, there is an extensive misuse of products that are illegally adulterated with diuretics, which has seriously increased health risks. Therefore, it is essential to develop an analytical method for the detection of adulterants in such substances. In this study, 23 diuretics, categorized into four groups, namely, thiazide diuretics (e.g., bendroflumethiazide), loop diuretics (e.g., bumetanide), potassium-sparing diuretics (e.g., amiloride), and carbonic anhydrase inhibitors (e.g., acetazolamide), were analyzed using ultrahigh-performance liquid chromatography-quadrupole orbitrap (UHPLC-Q-Orbitrap). Their fragmentation was elucidated based on the MS/MS data. The 124 products were screened by the UHPLC-Q-Orbitrap (LC-HRMS) method, and the confirmed compounds were quantitated by a previously established LC-MS/MS method. Approximately 5% of the samples were found to be illegally contaminated with diuretics at a concentration of 0.051-162 mg/g. The high selectivity and sensitivity of the UHPLC-Q-Orbitrap (LC-HRMS) method, in combination with the established fragmentation, offer a new approach for the rapid and accurate screening of diuretics in adulterated products, which would be ultimately beneficial for the public health.

Contribution of sewage to occurrence of phosphodiesterase-5 inhibitors in natural water

Phosphodiesterase-5 inhibitors (PDE-5i, such as Sildenafil, Tadalafil and Vardenafil, mainly prescribed to treat erectile dysfunction) and their generic drug equivalents have been widely marketed and consumed in Korea. From the concentrations detected in wastewater, we could deduce that relatively large amounts of PDE-5i were consumed without a legal prescription. Thus, PDE-5i’s presence in the environment via sewage is unavoidable, and their environmental fate within a sewage treatment plant (STP) should be evaluated. In this study, we investigated the occurrence of three PDE-5i analogs in the influent and effluent of two STPs and the receiving water bodies. The PDE-5i concentration in total reached 62 ± 12 (STP#1) and 88 ± 37 ng L⁻¹ (STP#2) in the sewage influent; about 70% of it was Sildenafil in both STPs. However, they were hardly removed by the STPs as the removal efficiency of the STPs was less than 10% ± 5%. Therefore, the pharmaceuticals were detected in the receiving water (lower than 7 ng L⁻¹as a total amount) and the concentration slightly increased downstream of the STPs. A simple mass balance model applied for the compounds in the STP effluent and receiving water bodies also confirmed that the discharged PDE-5i were quite persistent. Lastly, we identified temporal and regional patterns in the consumption of the drugs from daily variations of PDE-5i in the influent to these two STPs. For instance, the levels of PDE-5i in the sewage significantly increased on weekends (from Friday to Saturday), and especially in the area where adult-entertainment businesses are common. We estimated that the amount of PDE-5i consumption in this area was 31% higher than that in the area with fewer nightlife spots. Considering that they are pharmaceutically active and resistant to treatment processes within an STP, it is advised that a regular monitoring and management program for PDE-5i should be developed to prevent the discharge of the pharmaceuticals into the water environment.

Detection of 94 compounds related to sexual enhancement including sildenafil, tadalafil, vardenafil and their analogues in various formulations of dietary supplements and food samples using HPLC and LC-MS/MS

With an increase in the detection of structural and functional analogues of phosphodiesterase type 5 inhibitors (PDE-5i) in dietary supplements (DS) and foods, public health is threatened. Some products advertise natural ingredients despite containing PDE-5i that can cause serious adverse effects on human health. To avoid detection during routine screening, novel PDE-5i have been synthesised and added to DS and foods. The purpose of this study was to detect, identify, and quantify 94 PDE-5i and related compounds in DS and foods. Furthermore, the study investigated the detection cases and compared them by sample type, formulation, and compounds. The HPLC and LC-MS/MS methods were validated for limit of detection (LOD), limit of quantification (LOQ), linearity, and recovery in solid and liquid type samples. Both HPLC and LC-MS/MS showed satisfactory results, which were in conformance with the ICH guidelines. A total of 404 samples, including DS (99), and foods (305) were purchased from online and offline markets. Samples divided into 5 types of formulation were analysed; tablet, capsule, pilula (herbal medicine pill), powder and liquid type. Of these 130 samples (47 of 99 DS, and 83 of 305 foods) contained one or more PDE-5i or related compounds. Among the five types of formulation, the tablet type showed the highest detection rate (61.1%) in DS, whereas the capsule type showed the highest detection rate (53.8%) in food samples. This study will be helpful for monitoring illegal ED-related products, providing information to consumers, and ultimately contributing to protecting public health.

Fluorescence polarisation for high-throughput screening of adulterated food products via phosphodiesterase 5 inhibition assay

The surge in the consumption of food products containing herbal aphrodisiacs has driven their widespread adulteration. A rapid screening strategy is, therefore, warranted to curb this problem. This study established an enzyme inhibition assay to screen phosphodiesterase 5 (PDE5) inhibitors as adulterants in selected food products. Fluorescein-labelled cyclic-3',5'-guanosine monophosphate was utilised as substrates for the PDE5A1 enzyme, aided by the presence of nanoparticle phosphate-binding beads on their fluorescence polarisation. The sample preparation was optimised to improve the enzyme inhibition efficiency and applied to calculate the threshold values of six blank food matrices. The assay was validated using sildenafil, producing an IC₅₀ of 4.2 nM. The applicability of the assay procedure was demonstrated by screening 55 distinct food samples. The results were subsequently verified using confirmatory liquid chromatography-high-resolution mass spectrometry (LC-HRMS) analysis. Altogether, 49 samples inhibited the PDE5 enzyme above the threshold values (75.7%-105.5%) and were registered as potentially adulterated samples. The remaining six samples were marked as nonadulterated with percentage inhibition below the threshold values (-3.3%-18.2%). The LC-HRMS analysis agreed with the assay results for all food products except for the instant coffee premix (ICP) samples. False-positive results were obtained for the ICP samples at 32% (8/25), due to possible PDE5 inhibition by caffeine. Contrarily, all other food samples were found to produce 0% (0/30) false-positive or false-negative results. The broad-based assay, established via a simple mix-incubate-read format, exhibited promising potential for high-throughput screening of PDE5 inhibitors in various food products, except those with naturally occurring phosphodiesterase inhibitors such as caffeine.

Screening of Phosphodiesterase-5 Inhibitors and Their Analogs in Dietary Supplements by Liquid Chromatography-Hybrid Ion Trap-Time of Flight Mass Spectrometry

An accurate and reliable method based on ion trap–time of flight mass spectrometry (IT–TOF MS) was developed for screening phosphodiesterase-5 inhibitors, including sildenafil, vardenafil, and tadalafil, and their analogs in dietary supplements. Various parameters affecting liquid chromatographic separation and IT–TOF detection were investigated, and the optimal conditions were determined. The separation was achieved on a reversed-phase column under gradient elution using acetonitrile and water containing 0.2% acetic acid at a flow rate of 0.2 mL/min. The chromatographic eluents were directly ionized in the IT–TOF system equipped with an electrospray ion source operating in the positive ion mode. The proposed screening method was validated by assessing its linearity, precision, and accuracy. Sequential tandem MS was conducted to obtain structural information of the references, and the fragmentation mechanism of each reference was proposed for providing spectral insight for newly synthesized analogs. Structural information, including accurate masses of both parent and fragment ions, was incorporated into the MSⁿ spectral library. The developed method was successfully applied for screening adulterated dietary supplement samples.