A review of synthetic phosphodiesterase type 5 inhibitors (PDE-5i) found as adulterants in dietary supplements

Screening the quality of legal and illegal dietary supplements by LC-MS/MS

Dietary supplements are widely consumed. However, the lack of mandatory testing results in limited data on their quality, particularly in Eastern Europe. In this study, 21 legally registered and 9 illegal supplements, seized from an underground facility by the Polish Police, were examined. Contaminants were screened by utilising high-performance liquid chromatography coupled with untargeted mass spectrometry. The analysis identified 32 contaminants in the 30 dietary supplements examined. Untargeted analysis revealed a concerning issue: the intentional adulteration of both legal and illegal supplements with pharmacologically active substances that are prohibited in this category of products. This study indicated that many dietary supplements are of low quality due to deliberate adulteration or inadequate manufacturing conditions. The presence of unregistered or unapproved substances in these supplements poses serious health risks. Strong legal regulations are essential to address this issue effectively.

Benchtop NMR Coupled with Chemometrics: A Workflow for Unveiling Hidden Drug Ingredients in Honey-Based Supplements

Recently, benchtop nuclear magnetic resonance (NMR) spectrometers utilizing permanent magnets have emerged as versatile tools with applications across various fields, including food and pharmaceuticals. Their efficacy is further enhanced when coupled with chemometric methods. This study presents an innovative approach to leveraging a compact benchtop NMR spectrometer coupled with chemometrics for screening honey-based food supplements adulterated with active pharmaceutical ingredients. Initially, fifty samples seized by French customs were analyzed using a 60 MHz benchtop spectrometer. The investigation unveiled the presence of tadalafil in 37 samples, sildenafil in 5 samples, and a combination of flibanserin with tadalafil in 1 sample. After conducting comprehensive qualitative and quantitative characterization of the samples, we propose a chemometric workflow to provide an efficient screening of honey samples using the NMR dataset. This pipeline, utilizing partial least squares discriminant analysis (PLS-DA) models, enables the classification of samples as either adulterated or non-adulterated, as well as the identification of the presence of tadalafil or sildenafil. Additionally, PLS regression models are employed to predict the quantitative content of these adulterants. Through blind analysis, this workflow allows for the detection and quantification of adulterants in these honey supplements.

Analytical methods for the detection and characterization of unapproved phosphodiesterase type 5 inhibitors (PDE-5i) used in adulteration of dietary supplements- a review

This article is an up-to-date review of 112 unapproved phosphodiesterase type 5 inhibitors (PDE-5i) found as adulterants in sexual enhancement dietary supplements and other products from 2003 to July 2023. Seventy-five of these unapproved PDE-5i are analogues of sildenafil (67%), followed by 26 analogues of tadalafil (23%), 9 analogues of vardenafil (8%) and 2 other type of compounds (2%). The products have been formulated in various packaging, primarily in capsule, tablet, and powder forms. Common screening techniques allowing detection of such analogues include high performance or ultra-high performance liquid chromatography in tandem with ultra-violet detector (HPLC-UV or UPLC-UV) (50%) and thin-layer chromatography in tandem with ultra-violet detection (TLC-UV) (7%). Screening by mass spectrometry (MS) is relatively less common with the use of single-, triple-quadrupole or time-of-flight (TOF) mass spectrometers (9%). Meanwhile, the combined detection by UV-MS has been recorded at 10% usage. Screening by proton nuclear magnetic resonance spectroscopy (NMR) (11%) has also been applied. For compound characterization, i.e. structural elucidation, NMR spectroscopy has been preferred (100 out of 112 compounds), followed by high-resolution mass spectrometry (HRMS) (74 out of 112 compounds) and Fourier-transform infrared spectroscopy (FTIR) (44 out of 112 compounds). Over the past two decades, analytical technology has been evolving with enhanced sensitivity and resolution. Despite this, structural elucidation of the new emerging analogues in adulterated dietary supplements remains a challenge, especially when the analogues involve complex structural modification. Therefore, the above-mentioned techniques may not be adequate to characterize the analogues. Additional work involving chiroptical methods, two-dimensional (2D) NMR experiments and X-ray crystallography are likely to be required in the future.

A novel vardenafil analog in a healthcare product: Preparation, characterization, and quantification

OBJECTIVE

This study is aimed to develop a qualitative and quantitative method to detect a novel vardenafil analogue from a healthcare product, which is claimed to enhance sexual function. Method: The unknown compound was detected by non-targeted screening using ultra-high performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF-MS). MS2 spectra showed that the characteristic fragment ions of this unknown compound were highly similar to those of vardenafil. This compound was subsequently isolated by silica gel column chromatography and characterized by 1D (dimension) and 2D nuclear magnet resonance (NMR) specta, ultra-violet (UV) spectra, and fourier transform infrared (IR) spectra. A quantitative method for analyzing this identified compound in various healthcare product was developed based on high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS).

RESULTS

The unknown compound was identified as 2-(5-((4-ethylpiperazin-1-yl)sulfonyl)-2-propoxyphenyl)-5-methyl-7-propylimidazo.[5,1-f] [1,2,4]triazin-4(3H)-one based on the spectroscopic data. Quantitative results revealed that the matrix calibration curves of this compound had a good linear ranges of 2～50 ng/mL in pressed candy (R2 = 0.998), energy coffee (R2 = 0.999), and health wine (R2 = 0.997), respectively. The matrix effects, recoveries, and limit of quantitation (LOQ) of this compound all met the requirements of quantitative validation. Finally, the content of this compound in 5 batches of positive samples ranged from 1.24 to 7.20 g/kg. Conclusion: This study identified a novel vardenafil analog from a healthcare product and named it O-propyl vardenafil, and this compound was distinguished from vardenafil by the replacement of the ethyl group with a propyl group at the aryl alkyl ether moiety. Our developed quantitative method could meet practical needs. The high positive rate (16.67%) in 30 samples suggested that the related regulators should be alert to O-propyl vardenafil in routine test since it has not been detected ever before.

Isolation and identification of a novel vardenafil analogue, propoxy-vardenafil, found as an adulterant in a health supplement

Background

A novel vardenafil analogue was detected from a health wine claimed to be anti-impotence during a special inspection in an online store.

Methods

The unknown compound was found by using ultra-high performance liquid chromatography coupled to quadrupole time of flight mass spectrometry (UHPLC/Q-TOF MS). The characteristic product ions were similar to those of vardenafil. The UV spectrum of the compound closely mirrored that of vardenafil. The analogue underwent purification by semi-preparative HPLC and structurally identified by FT-IR and NMR analysis.

Results

Based on the data, The structure of the analogue was characterized as 2-[2-propyloxy-5-(4-ethylpiperazin-1-yl)sulfonylphenyl]-5-methyl-7-propyl-3H-imidazo [5,15,1-f] [1,2,4]triazin-4-one, simplified as propoxy-vardenafil.

Conclusion

To the best of our knowledge, the analogue has not been reported and is even only ninth vardenafil analogue, which was confirmed that a n-propyloxy group had replaced the ethoxy group on the aromatic ring of vardenafil. Therefore, It is essential to pay more attention to vardenafil analogues in the routine inspection of health supplements.

The POWER saga from 2007 to 2022: An example of a sexual enhancement dietary supplement tainted by different adulterants and still on the market

Ten POWER dietary supplements, chronologically called tabs, pills then caps, and advertised as 100% natural aphrodisiacs, were analyzed by ¹H NMR from 2007 to 2022. They were all tainted by PDE-5 inhibitors. Eight different adulterants were identified (sildenafil (1), sildenafil analogues (6), and vardenafil analogue (1)). Their amounts ranged from 15 to 145 mg/capsule. Four supplements contained at least 100 mg/capsule of PDE-5 inhibitor or analogue, the maximal recommended dose of sildenafil. The nature of the adulterant has changed over time, probably to evade its detection by regulatory agencies routine screening tests. Despite several warnings and/or seizures from several European food and/or health authorities, the dietary supplement POWER is still on sale on the Internet, thus demonstrating the impossibility of controlling this market. Faced with this situation, the consumer should be better informed by establishing at the European level a public database of tainted dietary supplements on the model of that of the US Food and Drug Administration. It should indicate the product name, its photo, the adulterant name, and be easily accessible to everyone.

Separation and structural elucidation of a novel vardenafil analogue as an adulterant in a natural health care dietary supplement

A novel vardenafil analogue was identified in dietary supplement as an adulterant in herbal formulations. The structure of this analogue was elucidated using HRMS, NMR after extraction from the pulverized powder. It was named morphardenafil as a morpholine ring has replaced the N-ethyl piperazine ring in vardenafil. A tablet of this dietary supplement contained about 50 mg of unspecified morphardenafil, which is 2.5 - 20-times the prescriptive dosage of Levetra, the commercial formulation of the vardenafil monohydrochloride salt in the market and probably places unwary consumers at risk for potentially serious adverse effects or drug-drug interaction (DDI).

Rapid screening of illegal additives in functional food using desorption electrospray ionization mass spectrometry imaging

Compounds such as Sildenafil, which bring potential health risks to consumers, have been illegally added to functional food. The public security department hopes to quickly screen for illegal additives. The quantity of seized samples is often large and their compositions are unknown; it is necessary to screen the unknown samples qualitatively and sometimes quantitatively. In this paper, a new method for rapid screening of 39 common illegal additives in six categories of functional food based on DESI-MSI technology is proposed, and the DESI-MSI library is established, which can be used for exclusive and sensitive qualitative confirmation of suspicious samples. A new carrier material that can be used for rapid qualitative detection of solid sample is discovered. The samples require simple or even no pretreatment to carry out high-resolution imaging through the imaging function of DESI-MSI. The imaging results are clear and intuitive, and can achieve fast and high-throughput qualitative identification of illegally added compounds. This method has good linearity, accuracy, precision, and little effect of matrix, so it can roughly quantify the illegal additives in functional products. Twenty-one batches of unknown samples were detected by DESI-MSI, and the positive results were confirmed by LC-MS/MS (QQQ). The results showed that the DESI-MSI method was effective and reliable. DESI-MSI with self-made database is a promising method for rapid screening of illegal additives in functional food, which can be widely used in grass-roots police stations.

Development of a detector tube for screening tadalafil and its analogues in adulterated sexual enhancement products

Sexual enhancement products adulterated with phosphodiesterase 5 inhibitors (PDE-5i) pose a serious public health concern. Tadalafil and its analogues (Tds) are PDE-5i frequently detected as adulterants. In this study, a Td detector tube for the rapid detection of Tds was developed based on the color change reaction between sulfuric acid and Tds. The specificity of this test method was evaluated using 13 Tds, all of which elicited positive results. Additionally, 30 commonly found adulterants in dietary supplements, 11 active pharmaceutical ingredients of psychotropic drugs and 18 food ingredients were tested and obtained no false-positive results, except levomepromazine. The test tube accurately detected the presence or absence of Tds in 54 commercially available products. The visual detection limit was 2-50 and 5-20 μg/ml for Tds and tadalafil-spiked samples with matrix, respectively. The applicability of the developed detector tube to a semiquantitative test using digital image analyses were investigated using red, green, and blue color values. The results of the recovery test suggested that the tube test was affected by the dark-colored matrix. The results of semiquantitative analyses of tadalafil for five marketed products were consistent with the liquid chromatographic quantification results, except for the blue value. The detector tube developed in this study can facilitate with the rapid screening of Tds in adulterated sexual enhancement products.

Mechanisms and Health Aspects of Food Adulteration: A Comprehensive Review

Food adulteration refers to the alteration of food quality that takes place deliberately. It includes the addition of ingredients to modify different properties of food products for economic advantage. Color, appearance, taste, weight, volume, and shelf life are such food properties. Substitution of food or its nutritional content is also accomplished to spark the apparent quality. Substitution with species, protein content, fat content, or plant ingredients are major forms of food substitution. Origin misrepresentation of food is often practiced to increase the market demand of food. Organic and synthetic compounds are added to ensure a rapid effect on the human body. Adulterated food products are responsible for mild to severe health impacts as well as financial damage. Diarrhea, nausea, allergic reaction, diabetes, cardiovascular disease, etc., are frequently observed illnesses upon consumption of adulterated food. Some adulterants have shown carcinogenic, clastogenic, and genotoxic properties. This review article discusses different forms of food adulteration. The health impacts also have been documented in brief.

Scaffold Repurposing Reveals New Nanomolar Phosphodiesterase Type 5 (PDE5) Inhibitors Based on Pyridopyrazinone Scaffold: Investigation of In Vitro and In Silico Properties

Inhibition of PDE5 results in elevation of cGMP leading to vascular relaxation and reduction in the systemic blood pressure. Therefore, PDE5 inhibitors are used as antihypertensive and antianginal agents in addition to their major use as male erectile dysfunction treatments. Previously, we developed a novel series of 34 pyridopyrazinone derivatives as anticancer agents (series A–H). Herein, a multi-step in silico approach was preliminary conducted to evaluate the predicted PDE5 inhibitory activity, followed by an in vitro biological evaluation over the enzymatic level and a detailed SAR study. The designed 2D-QSAR model which was carried out to predict the IC₅₀ of the tested compounds revealed series B, D, E and G with nanomolar range of IC₅₀ values (6.00–81.56 nM). A further docking simulation model was performed to investigate the binding modes within the active site of PDE5. Interestingly, most of the tested compounds showed almost the same binding modes of that of reported PDE5 inhibitors. To validate the in silico results, an in vitro enzymatic assay over PDE5 enzyme was performed for a number of the promising candidates with different substitutions. Both series E and G exhibited a potent inhibitory activity (IC₅₀ = 18.13–41.41 nM). Compound 11b (series G, oxadiazole-based derivatives with terminal 4-NO₂ substituted phenyl ring and rigid linker) was the most potent analogue with IC₅₀ value of 18.13 nM. Structure–activity relationship (SAR) data attained for various substitutions were rationalized. Furthermore, a molecular dynamic simulation gave insights into the inhibitory activity of the most active compound (11b). Accordingly, this report presents a successful scaffold repurposing approach that reveals compound 11b as a highly potent nanomolar PDE5 inhibitor worthy of further investigation.

Hierarchical clustering of liquid chromatography-tandem mass spectrometry data for screening of phosphodiesterase type 5 inhibitors and their analogues in adulterated dietary supplements

Sexual enhancement dietary supplements have often been adulterated with phosphodiesterase type 5 (PDE-5) inhibitors used for treatment of erectile dysfunction, and widely distributed through online markets. As the illegal adulterants, the original PDE-5 inhibitor drugs and a numerous number of synthetized analogues, more than 80, have already been found. Therefore, analytical methods that detect various PDE-5 inhibitors and uncover newly synthesized analogues are needed. In this study, we have developed a rapid and reliable screening method for PDE-5 inhibitors and their structural analogues by using liquid chromatography-tandem mass spectrometry (LC-MS/MS) followed by hierarchical clustering based on similarity of MS/MS spectra. Forty reference standards of PDE-5 inhibitors/analogues were measured using a quadrupole-orbitrap mass spectrometer in data-dependent mode. The 60 most intense fragment ions were extracted from each MS/MS spectra, and the ions observed within 1.5 mDa mass tolerance were considered to be the same ion. Based on fragment ion tables representing detected ions for each compound, hierarchical clustering was performed. The resulting dendrogram showed that the reference standards were separated into seven clusters according to their characteristic structures. Subsequently, two additional standards spiked into a herbal sample were analyzed. While herbal components were clearly separated from the clusters of the reference standards, the spiked standards were clustered closely with the structurally similar standards. Furthermore, application of our method to dietary supplements allowed for detection of sildenafil and tadalafil as adulterants. These results suggest that our screening method facilitates discovery of adulterant PDE-5 inhibitors/analogues by illustrating their structural similarity.

Identification of phosphodiesterase type-5 (PDE-5) inhibitors in herbal supplements using a tiered approach and associated consumer risk

The use of herbal supplements for improved sexual performance is a common practice amongst the youth and some senior citizens in Ghana. These products are considered 'natural' and greatly preferred over synthetic alternatives due to the assurance of little to no adverse effects by producers. However, the high rate of adulteration often compromises their safety. Forty herbal supplements, of which 25 were previously shown to result in medium to high intake of phosphodiesterase type-5 (PDE-5) inhibitors using a PDE-Glo bioassay, were further investigated using liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis to examine the reliability of the bioassay and whether the observed higher responses could be ascribed to inherent plant constituents or adulterants. Results showed significant amounts of vardenafil, tadalafil and especially sildenafil, in 2, 1 and 10 samples, respectively, with total concentration levels resulting in estimated daily intakes (EDIs) above 25 mg sildenafil equivalents with six supplements even having EDIs above 100 mg sildenafil equivalents. Only one sample contained a natural ingredient (icariin), but its concentration (0.013 mg g^-1) was too low to explain the observed potency in the bioassay. The estimated concentrations of PDE-5 inhibitors in 35 supplements, according to the bioassay, were in line with those of the LC-MS/MS analysis. However, discrepancies were observed for five supplements. Further examination of one of the latter supplements using the PDE-Glo bioassay to select the positive fraction and further examination with LC-MS/MS and ¹H-NMR revealed the presence of hydroxythiohomosildenafil, a sildenafil analogue not yet included in the liquid chromatography-mass spectrometry reference library. This study demonstrates the significance of applying a tiered approach, where the use of a bioassay is followed by chemical analysis of bioactive samples in order to identify unknown bioactive compounds.

Rapid screening of illegal additives in functional food using atmospheric pressure solids analysis probe coupled to a portable mass spectrometer

Pharmaceutical drugs like Sildenafil are illegally added to functional food such as nutritional supplements and herbal remedies to deliver drugs without a regular prescription to consumers. Rapid screening of illegal additives is desirable for the public security department. The seized samples are often large in number and unknown in composition; methods are needed for qualitative screening of unknown samples. Here, a new approach is presented based on atmospheric pressure solids analysis probe (ASAP) coupled with single-quadrupole mass spectrometer to rapidly screen 42 common illegal additives in six categories of functional food. The ASAP-MS method could be applied to solid or liquid sample analysis with a very simple pre-treatment and no LC chromatographic separation, using a home-built library; the identification of suspicious additives could be obtained rapidly. More importantly, the approach is sensitive enough for complex matrix samples like coffee samples. 21 batches of seized unknown samples were tested by the ASAP-MS, and the positive results were confirmed by LC-MS/MS(QQQ), indicating that the ASAP-MS method is effective and reliable. The ASAP-MS with home-built library is a promising method for rapid screening of illegal additives in functional food, which could be widely used in the grassroots police station that lack professional laboratory environment.

Improved molecular softness of tadalafil hapten enhancing antibody performance in immunoassay: Evidence from computational chemistry

The tadalafil-like compounds have appeared recently as adulterants in drinks and healthcare dietary supplements sourced from medicinal and edible food, which may cause illness and even death. In this work, the rationality of haptens was explored by computational chemistry and molecular simulation theories such as frontier molecular orbital (FMO)-based softness (S), three-dimensional (3D) structure, surface electrostatic potential (ESP), and lipophilic potential (LP). An antiserum from hapten H5 with the highest softness and maintaining the appropriate three-dimensional (3D) structure showed the optimal immunoassay performance, indicating an increasing softness was a critical factor for effective hapten. Based on the antibody induced by hapten H5, an indirect competitive enzyme-linked immunosorbent assay (icELISA) method for detecting multiple tadalafil-like adulterants was established. The icELISA showed a limit of detection (LOD), 50% inhibition concentration (IC₅₀ ), and a working range of 0.004-0.396, 0.89-4.27, and 0.094-16.71 ng/ml for tadalafil, amino tadalafil, acetamino tadalafil, nortadalafil, and N-desmethyl ent-tadalafil, respectively. The spiked recoveries of tadalafil-like adulterants in samples ranged from 84.9% to 116.2%. The results of the icELISA and HPLC-MS/MS methods had a good correlation for real samples with the R² of 0.9955. Specially, this work not only provided a convenient immunoassay method for measuring tadalafil-like adulterants in spirit drinks and dietary supplements in group-screening manner, but also suggested that softness was likely to be a general theory for rational hapten design. PRACTICAL APPLICATION: Rapid monitoring of tadalafil-like adulterants in food samples is very necessary and important for consumers, regulatory agencies, and the food industry.

Recent applications of phosphodiesterase (PDE5) inhibition assays for detecting adulterated sexual enhancement products

Consumer products marketed for sexual enhancement are frequently adulterated with erectile dysfunction (ED) drugs and analogs; consuming these undisclosed adulterants can pose significant health hazards. Although ED drugs/analogs have unpredictable and diverse structures that pose challenges for detecting them, they all share the ability to inhibit phosphodiesterase-5 (PDE5) activity, a pharmacological mechanism responsible for their effects. Consequently, several PDE5 inhibition assays have been recently applied as screening methods to detect ED drug/analogs in products. Here, the successes and challenges are highlighted for screening sexual enhancement products by PDE5 inhibition assays.

Isolation and characterization of N-phenyl propoxyphenyl carbodenafil from an illegal coffee powder product

A new carbodenafil-like compound, N-phenyl propoxyphenyl carbodenafil has been identified from an illegal coffee powder product. It was isolated using a semi-preparative liquid chromatography column. The presence of a propoxy group at the aryl alkyl ether moiety, and the direct bonding of a phenyl group to piperazine ring have been unambiguously characterized by ultra-violet (UV), Fourier transform infrared (FTIR), high-resolution mass spectrometry (HRMS) and nuclear magnet resonance (NMR) analysis.

Selectivity of identification of compounds from the group of phosphodiesterase-5 inhibitors (PDE-5i) in falsified products from the Polish market using attenuated total reflectance Fourier transform infrared spectroscopy and X-ray powder diffraction

Falsified drugs are a growing problem and a great threat all over the world. Searching for easy, fast, not expensive and reproducible methods for identification of active pharmaceutical ingredients (APIs) is an important issue. The application of ATR-IR technique for identification of phosphodiesterase-5 inhibitors (PDE-5i) in falsified products from the Polish market has been demonstrated. Furthermore, the strategy of confirmation of the product's originality inaquick and easy way has been developed. The advantages of this application are: exceptional simplicity, very short measurement time, high selectivity inrelation to structurally similar substances and almost no sample preparation. After validation, developed strategy has been successfully introduced into routine analysis.

Contribution to the Detection of Poor Quality Sildenafil Drugs in Burkina Faso Using High-Performance Thin-Layer Chromatography

In substandard drugs enforcement, there is a need to develop reliable, fast, and inexpensive analytical methods. Due to its very characteristics, HPTLC offers opportunities for the development of methods that meet these requirements. This technique was used to develop and validate a method for the determination of sildenafil in pharmaceutical formulations from the licit and illicit supply chain in Burkina Faso. Taking into account optimization parameters such as measurement wavelength and mobile phase composition, the best elution quality is found at the maximum signals of spots on silica plates at 305 nm, using a mixture of dichloromethane-methanol mixture 9 : 1 (v/v) proportions. The method developed under these conditions was validated using the accuracy profile as a decision tool. The establishment of the response function curves allowed the choice of the polynomial function applied to the peak areas. This mathematical model provides a validity range between 0.4 and 0.6 mg/mL. The application of the developed and validated method to collected samples allowed the detection of two substandard drugs and confirmed the poor quality of drugs in the illicit market. More data using this approach in a variety of drug molecules could lead to the establishment of databases of counterfeit drugs in Burkina Faso.

Rapid Screening and Quantitative Determination of Illegal Phosphodiesterase Type 5 Inhibitors (PDE-5i) in Herbal Dietary Supplements

Phosphodiesterase type 5 inhibitors (PDE-5i) are the first-line medication for oral erectile dysfunction, which are used according to the prescription of doctors. However, these substances have been found illegally in supplementary foods. The quality and safety of dietary supplements for enhancing male sexual performance have been questioned, raising the need for continual development of analytical methods. Liquid chromatography coupled with high-resolution mass spectrometry has become one of the most effective methods to identify and measure PDE-5i concentration. In this research, we focused on (i) developing and validating an effective screening and quantitation method for more than 53 PDE-5i in ingredients and supplementary products using LC-Q-Exactive after a simple sample extraction and (ii) assessing PDE-5i content in natural-based supplementary products available in Vietnam market. The extraction method used a small amount of organic solvent, which makes it more environmentally friendly (greener). The developed method has a limit of detection of 0.4 mg/kg, a limit of quantitation of 1.2 mg/kg, recoveries from 80 to 110%, and repeatability lower than 15%. Ninety-two herbal supplementary foods and ingredients used for enhancement of male sexual performance available in Vietnamese markets were collected. Fourteen PDE-5i including conventional and novel analogous were detected and measured in eighteen food supplements and two formulation ingredient samples.

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.

Development of a group-specific antibody-based immunoassay method for simultaneously detecting sildenafil-like adulterants in herbal spirit drinks

Phosphodiesterase type 5 (PDE-5) inhibitors are commonly used to treat erectile dysfunction. There is a problem with synthesis and illegal use of a wide range of analogues of the licenced drugs and a simple class-wide analytical method is required. In this work, based on structural modelling, we developed an immunological method using norneovardenafil as a hapten as it contains only the general sub-structure and the common features of sildenafil-like adulterants, such as hydrophobic centres, hydrogen-bond donor atoms and hydrogen-bond acceptor atoms. Thus theoretically it could induce production of antibody which could recognise multiple sildenafil-like adulterants. By immunising rabbits, a group-specific polyclonal antibody was obtained with the desired broad-spectrum molecular recognition performance against sildenafil-like adulterants. Then, an indirect competitive enzyme-linked immunosorbent assay (icELISA) was developed for the detection of sildenafil-like adulterants in herbal spirit drinks. Under the optimised conditions, the icELISA method showed broad linear ranges for acetildenafil, sildenafil and vardenafil respectively of 0.7 to 27.7 μg/kg, 1.0 to 70.7 μg/kg and 1.5 to 22.7 μg/kg, with half-maximal inhibition concentration (IC₅₀) values of 4.5 μg/kg, 8.3 μg/kg and 5.7 μg/kg, respectively. For eleven herbal spirit drinks, there was good agreement between total levels of sildenafil-like adulterants measured by icELISA and levels of each of four individual adulterants determined by LC-MS/MS. In short, the developed icELISA can be employed for rapid and simple screening for adulteration of herbal spirit drinks with sildenafil-like compounds.

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.

Drug adulteration of sexual enhancement supplements: a worldwide insidious public health threat

Worldwide, the consumption of dietary supplements for the enhancement of sexual performance is common. Consumers are generally fond of these products because they often want to avoid drugs, preferring "natural" than "chemical" solutions. This is challenging, as many of these supplements labelled "herbal" or "natural" are actually adulterated with drugs, mainly phosphodiesterase-5 inhibitors. This phenomenon is facilitated by fewer demanding regulations for marketing supplements. Thus, consumers may be widely exposed to serious adverse events, such as acute liver injury, kidney failure, pulmonary embolism, stroke or even death. We aim to warn physicians about this issue. This multidisciplinary review simultaneously deals with clinical consequences of this phenomenon, analytical toxicology and regulation. Indeed, after outlining this worldwide issue and highlighting that a drug-adulterated dietary supplement is actually a falsified drug, we discuss its main contributing factors. Then, we describe some examples of adverse events of which a case of sildenafil-tadalafil-induced ischaemic stroke that benefited medical care in our hospital. Furthermore, we present some means to avoid adulteration and discuss their limitations that may be explained by the heterogeneity of the regulation of dietary supplements between countries. Doing so, we point out the requirement of a global harmonization of this regulation for an efficient eradication of this public health threat. Meanwhile, dietary supplements should be considered adulterated until proven otherwise. Thus, we encourage physicians to investigate these products in the drug histories of their patients, especially when clinical conditions cannot be explained by classical aetiologies.

Diketopiperazine-Based, Flexible Tadalafil Analogues: Synthesis, Crystal Structures and Biological Activity Profile

Phosphodiesterase 5 (PDE5) is one of the most extensively studied phosphodiesterases that is highly specific for cyclic-GMP hydrolysis. PDE5 became a target for drug development based on its efficacy for treatment of erectile dysfunction. In the present study, we synthesized four novel analogues of the phosphodiesterase type 5 (PDE5) inhibitor-tadalafil, which differs in (i) ligand flexibility (rigid structure of tadalafil vs. conformational flexibility of newly synthesized compounds), (ii) stereochemistry associated with applied amino acid building blocks, and (iii) substitution with bromine atom in the piperonyl moiety. For both the intermediate and final compounds as well as for the parent molecule, we have established the crystal structures and performed a detailed analysis of their structural features. The initial screening of the cytotoxic effect on 16 different human cancer and non-cancer derived cell lines revealed that in most cases, the parent compound exhibited a stronger cytotoxic effect than new derivatives, except for two cell lines: HEK 293T (derived from a normal embryonic kidney, that expresses a mutant version of SV40 large T antigen) and MCF7 (breast adenocarcinoma). Two independent studies on the inhibition of PDE5 activity, based on both pure enzyme assay and modulation of the release of nitric oxide from platelets under the influence of tadalafil and its analogues revealed that, unlike a reference compound that showed strong PDE5 inhibitory activity, the newly obtained compounds did not have a noticeable effect on PDE5 activity in the range of concentrations tested. Finally, we performed an investigation of the toxicological effect of synthesized compounds on Caenorhabditis elegans in the highest applied concentration of 6a,b and 7a,b (160 μM) and did not find any effect that would suggest disturbance to the life cycle of Caenorhabditis elegans. The lack of toxicity observed in Caenorhabditis elegans and enhanced, strengthened selectivity and activity toward the MCF7 cell line made 7a,b good leading structures for further structure activity optimization and makes 7a,b a reasonable starting point for the search of new, selective cytotoxic agents.

Novel synthesized attapulgite nanoparticles-based hydrophobic monolithic column for in-tube solid-phase microextraction of thiosildenafil, pseudovardenafil, and norneosildenafil in functional foods

In this study, a novel method which involved in-tube solid-phase microextraction (SPME) using an attapulgite (ATP) nanoparticles-based hydrophobic monolithic column was successfully developed. It was coupled with high-performance liquid chromatography-ultraviolet detection for the determination of three phosphodiesterase-5 (PDE-5) inhibitors, including thiosildenafil, pseudovardenafil, and norneosildenafil, in functional foods. The monolithic column was prepared by one-step polymerization, using 3-trimethoxysilylpropyl methacrylate-modified ATP nanoparticles and 1-butyl-3-vinylimidazolium bromide (VBIMBr) as the functional monomers, and ethylene glycol dimethacrylate (EDMA) as the cross-linker. The obtained poly(ATP-VBIMBr-EDMA) monolith was characterized by scanning electron microscopy equipped with energy-dispersive analysis of X-ray, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction. The adsorption capacity, up to 2.00 μg/cm calculated by the Langmuir isotherm model, was about six times that of the poly(VBIMBr-EDMA) monolith. Crucial factors affecting the extraction efficiency, including sample solvent, elution solvent, flow rates of sampling loading and elution, sample loading volume, and elution volume, were investigated in details. Under the optimal in-tube SPME conditions, the proposed method showed good reproducibility with run-to-run, column-to-column, and batch-to-batch relative standard deviations less than 7.2%, and low limits of detection of 0.5-0.9 ng/mL in real samples. Thiosildenafil was detected in four types of functional foods with the contents of 1.30-4.78 μg/g. This newly proposed in-tube SPME method based on poly(ATP-VBIMBr-EDMA) monolith may provide a simple, efficient, and promising alternative to daily monitoring of PDE-5 inhibitors in functional foods.

A Mass Spectrometry Based Metabolite Profiling Workflow for Selecting Abundant Specific Markers and Their Structurally Related Multi-Component Signatures in Traditional Chinese Medicine Multi-Herb Formulae

In Traditional Chinese Medicine (TCM), herbal preparations often consist of a mixture of herbs. Their quality control is challenging because every single herb contains hundreds of components (secondary metabolites). A typical 10 herb TCM formula was selected to develop an innovative strategy for its comprehensive chemical characterization and to study the specific contribution of each herb to the formula in an exploratory manner. Metabolite profiling of the TCM formula and the extract of each single herb were acquired with liquid chromatography coupled to high-resolution mass spectrometry for qualitative analyses, and to evaporative light scattering detection (ELSD) for semi-quantitative evaluation. The acquired data were organized as a feature-based molecular network (FBMN) which provided a comprehensive view of all types of secondary metabolites and their occurrence in the formula and all single herbs. These features were annotated by combining MS/MS-based in silico spectral match, manual evaluation of the structural consistency in the FBMN clusters, and taxonomy information. ELSD detection was used as a filter to select the most abundant features. At least one marker per herb was highlighted based on its specificity and abundance. A single large-scale fractionation from the enriched formula enabled the isolation and formal identification of most of them. The obtained markers allowed an improved annotation of associated features by manually propagating this information through the FBMN. These data were incorporated in the high-resolution metabolite profiling of the formula, which highlighted specific series of related components to each individual herb markers. These series of components, named multi-component signatures, may serve to improve the traceability of each herb in the formula. Altogether, the strategy provided highly informative compositional data of the TCM formula and detailed visualizations of the contribution of each herb by FBMN, filtered feature maps, and reconstituted chromatogram traces of all components linked to each specific marker. This comprehensive MS-based analytical workflow allowed a generic and unbiased selection of specific and abundant markers and the identification of multiple related sub-markers. This exploratory approach could serve as a starting point to develop more simple and targeted quality control methods with adapted marker specificity selection criteria to given TCM formula.

Isolation and identification of ten new sildenafil derivatives in an alleged herbal supplement for sexual enhancement

A sexual enhancer dietary supplement in pre-commercialization phase was analyzed. It contained the two phosphodiesterase-5 inhibitors (PDE-5i) sildenafil and methisosildenafil as major adulterants. Fourteen more sildenafil derivatives were detected and after isolation, their structures were elucidated thanks to NMR, high resolution and tandem mass spectrometry, and UV spectroscopy. Ten of them were never described. All these compounds are probably by-products of different reaction steps during the synthesis of the two PDE-5i that were not properly eliminated during the purification procedure. The total amount of sildenafil-related compounds was estimated at 68 mg per capsule, sildenafil and methisosildenafil accounting for 20 mg and 38 mg respectively.

Microwave-assisted extraction followed by salting-out phase separation for hierarchical screening of illegal adulterants in aphrodisiac health products by multi-dimensional fingerprint profiling analysis

A novel method for hierarchical screening of illegal adulterants in Fur seal ginseng pills (FSGP) products was developed by microwave-assisted extraction (MAE) coupled to salting-out assisted liquid-liquid extraction (SALLE) with multi-dimensional fingerprint profiling analysis. Using a homogeneous system formed by dimethyl carbonate (DMC) and water as the extractant, the MAE conditions were investigated to maximize extraction recoveries, followed by addition of ammonium sulfate to induce DMC phase separation for SALLE enrichment of 16 potentially illegal adulterants such as phosphodiesterase type-5 inhibitors, androgens, α receptor antagonists and yohimbine etc. By means of high-performance liquid chromatography (HPLC) with diode array detection (DAD) and fluorescence detection (FLD), multi-dimensional fingerprints were acquired by multi-wavelength detection to highlight the signals of the potentially illegal adulterants and reduce or remove interferences from the sample matrix. For high accuracy and reliability, a hierarchical screening strategy was designed by multi-dimensional fingerprinting profiling analysis (MDFPA). The method exhibited proper identification and quantification performance, and it was successfully applied to screening of illegal adulterants in 18 batches of the samples through the step-by-step MDFPA. Also, the results were further confirmed by ultra high-performance liquid chromatography-quadrupole-orbitrap mass spectrometry (UHPLC-Q-Orbitrap/MS). The proposed method was proved to be a green, efficient and reliable alternative to monitoring aphrodisiac health products.

Structure elucidation of a PDE5 inhibitor detected as an illegal adulteration in a libido-boosting dietary supplement

A compound with potent inhibitory activity for phosphodiesterase type 5 (PDE5) was identified as an illegal adulteration in a libido-boosting dietary supplement being sold at a store in Tokyo. This compound was identified as 5,6-diethyl-2-{5-[(4-methylpiperazin-1-yl)sulphonyl]-2-propoxyphenyl}pyrimidin-4(3H)-one using liquid chromatography-diode array detector (LC-DAD), liquid chromatography-tandem mass spectrometer (LC-MS), LC-HRMS, nuclear magnetic resonance (NMR), and X-ray crystallography. The IC₅₀ value of the inhibitory activity for PDE5A1 (one of the PDE5 isoforms) was 2.0 nM (sildenafil IC₅₀ value was 4.5 nM). This compound was previously synthesised as a PDE5 inhibitor by Shanghai Institute of Materia Medica. The dietary supplement contained 85 mg of this compound in a capsule, which was about 26% of the capsule content (320 mg).

Interpol review of controlled substances 2016-2019

This review paper covers the forensic-relevant literature in controlled substances from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20Review%20Papers%202019.pdf.

[LC/Tribrid Orbitrap Analysis of Phosphodiesterase-5 Inhibitors and Their Analogs as Adulterants in Dietary Supplements]

LC/Tribrid Orbitrap was developed to determine phosphodiesterase-5 (PDE-5) inhibitors and their analogs as adulterants in dietary supplements. High-resolution MS/MS and MS³ spectra of PDE-5 inhibitors and their analogs were obtained by LC/Tribrid Orbitrap using both higher-energy collisional dissociation and collision-induced dissociation. We investigated dietary supplements that claim to enhance men's sexual performance, and detected PDE-5 inhibitors and their analogs. We also estimated the structures of the PDE-5 inhibitor analogs and the impurities of PDE-5 inhibitors and their analogs in the dietary supplements.

Instrumental neutron activation analysis (INAA) and liquid chromatography (LC) coupled to high resolution mass spectrometry (HRMS) characterisation of sildenafil based products seized on the Italian illegal market

The commerce of illegal and counterfeit medicinal products on internet is a serious criminal problem. Drugs for erectile dysfunction such as phosphodiesterase type 5 inhibitor are the most commonly counterfeited medicines in Europe. The search of possible toxic chemical substances in seized products is needed. Moreover, the profiling of the material can be the source of relevant forensic information. For the first time a combined approach based on liquid chromatography (LC) coupled to high resolution mass spectrometry (HRMS) and instrumental neutron activation analysis (INAA) is proposed and tested, allowing characterisation of both authentic and illegal pharmaceuticals containing sildenafil seized in Italy. LC-HRMS allowed the detection and identification of unknown impurities not reported on labels in illegal products and the quantitation of the sildenafil. INAA showed to be suitable to provide both qualitative and quantitative information for forensic purposes on 23 elements, allowing discrimination between legal and illegal products.

Revisiting the halogen bonding between phosphodiesterase type 5 and its inhibitors

Halogenated ligands are nowadays commonly designed in order to increase their potency against protein targets. Although novel computational methods of evaluating the affinity of such halogenated inhibitors have emerged, they still lack the sufficient accuracy, which is especially noticeable in the case of empirical scoring functions, being the method of choice in the drug design process. Here, we evaluated a series of halogenated inhibitors of phosphodiesterase type 5 with ab initio methods, revealing the physical nature of ligand binding and determining the components of interaction energy that are essential for proper inhibitor ranking. In particular, a nonempirical scoring model combining long-range contributions to the interaction energy provided a significant correlation with experimental binding potency, outperforming a number of commonly used empirical scoring functions. Considering the low computational cost associated with remarkable predictive abilities of the aforementioned model, it could be used for rapid assessment of the ligand affinity in the process of rational design of novel halogenated compounds.

Characterization of a new illicit phosphodiesterase-type-5 inhibitor identified in the softgel shell of a dietary supplement

A new sildenafil analog has been identified in the softgel shell of a dietary supplement. The compound was investigated by UV spectroscopy and high-resolution MS analysis, leading to the proposed structure 1-methyl-5-{5-[2-(4-methylpiperazin-1-yl)acetyl]-2-propoxyphenyl}-3-propyl-1,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one. A synthetic reference compound with the proposed structure was prepared, and the two sets of analytical data were compared, confirming the structure of the new compound. The compound was named propoxyphenyl noracetildenafil from its structure and similarity with the known compound.

Common risks of adulterated and mislabeled herbal preparations

Due to the growing trend of returning to nature and the fear of adverse reactions from conventional medicines, people are increasingly resorting to the use of herbal preparations. Because of long-term use and natural origin these preparations give a sense of security. But herbal formulations also possess undesirable effects and, among other dangers, present a risk connected with deliberate addition of synthetic compounds, deliberate or unintentional replacement of the plant species or simply a risk of mislabeling. While the replacement of the plant species occurs in a very different groups of herbal products, reports of added illicit synthetic substances often include groups of herbal weight-loss preparations, sexual enhancers, preparations for treatment of rheumatic and inflammatory diseases, antidiabetic and blood pressure lowering preparations. In the world of Internet ordering, these are the dangers that everyone should be aware of. In this article, we reviewed the safety issues related to adulterated or mislabeled herbal products.