Identification of new synthetic PDE-5 inhibitors analogues found as minor components in a dietary supplement

Variable temperature-nuclear magnetic resonance experiment and high-resolution MS/MSn measurement of hydroxycarbodenafil, and its PDE5 inhibitory activity

Hydroxycarbodenafil, an analogue of carbodenafil, was detected in a dietary supplement in China in 2020. However, previous reports have not identified some carbon signals from the piperazine ring in nuclear magnetic resonance (NMR) experiments. Because the compound contains an amide bond, the reaction was suggested to be characteristic of compounds with rotational isomers. Variable-temperature NMR is used to determine the rotational barrier between different conformations by changing the measurement temperature. Using this technique, we succeeded in obtaining the first distinct data, including the carbon signals of the piperazine ring in the NMR spectrum of hydroxycarbodenafil. We also confirmed that this technique could be applied to other carbodenafil analogues. Multi-stage mass spectrometry (MSn) measurements with a high-resolution mass spectrometer specific to the substructures were performed to develop a protocol for the structural determination of the carbodenafil analogues. In addition, hydroxycarbodenafil was analysed using X-ray crystallography, and its inhibitory activity against phosphodiesterase type 5 (PDE5) was measured. The IC50 value of the inhibitory activity of hydroxycarbodenafil for PDE5A1, a PDE5 isoform, of 2.9 nM was lower than the 4.5 nM for sildenafil, a positive control.

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 multi-analyte screening method for the rapid detection of illicit adulterants in dietary supplements using a portable SERS analyzer

The popularity and number of dietary supplements on the health market have experienced an unprecedented boost in recent years. Simultaneously, their increased use has been accompanied by an increase in acute intoxication cases linked to the adulteration of these products with illicit and undeclared substances. In this study, a SERS-based screening methodology was developed to rapidly detect illegally added pharmaceutically active substances to dietary supplements. A portable analyzer and silver printed-SERS substrates were used to enhance the signal, requiring less than 20 min of sample preparation prior to the analysis. The method was successful in the qualitative identification of eleven out of twenty-three illicit adulterants in the dietary supplements; it could detect the target compounds at realistic adulteration levels (0.1-5.0% w/w), demonstrating the potential of SERS-based methodologies for forensic rapid screening applications. The developed method is quick, easy to use, requires no skilled technicians and little sample preparation, and allows in-situ analyses. For these reasons, it is suitable for quick screening to be performed by inspectors at customs. Moreover, the low specificity of spectroscopic methods, to which SERS belongs, would benefit the detection of newly synthesized analogues of the target adulterants, which would otherwise be more difficult using common mass spectrometry methods in absence of reference standards.

Assessment of Undeclared Synthetic Drugs in Dietary Supplements in an Analytical View: A Comprehensive Review

Dietary supplements have gained widespread attention globally as they are supposed to be healthier than synthetic pharmaceutical compounds with fewer side effects. Unlike common prescription drugs, dietary supplements are readily available to the general public. However, over the past few years, all kinds of legal and illegal drugs, have been detected in dietary supplements without labeling to defraud consumers, resulting in serious public health consequences. Due to the increasing number of drug frauds in dietary supplements, their consumption will undoubtedly risk consumers. Therefore; the importance of high-tech analytical methods in their assessment for controlling food quality seems undeniable. The current review examines the analytical techniques that focus on adulterating health products with undeclared pharmaceuticals, including registered and banned drugs. The present study referred to a survey from 2004 to 2021 based on articles in the Scopus database.

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.

[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.

Fighting falsified medicines: The analytical approach

Given the harm to human health, the fight against falsified medicines has become a priority issue that involves numerous actors. Analytical laboratories contribute by performing analyses to chemically characterise falsified samples and assess their hazards for patients. A wide range of techniques can be used to obtain individual information on the organic and inorganic composition, the presence of an active substance or impurities, or the crystalline arrangement of the formulation's compound. After a presentation of these individual techniques, this review puts forward a methodology to combine them. In order to illustrate this approach, examples from the scientific literature (products used for erectile dysfunction treatment, weight loss and malaria) are placed in the centre of the proposed methodology. Combining analytical techniques allows the analyst to conclude on the falsification of a sample, on its compliance in terms of pharmaceutical quality and finally on the safety for patients.

A chemical family-based strategy for uncovering hidden bioactive molecules and multicomponent interactions in herbal medicines

Two concepts involving natural products were proposed and demonstrated in this paper. (1) Natural product libraries (e.g. herbal extract) are not perfect for bioactivity screening because of the vast complexity of compound compositions, and thus a library reconstruction procedure is necessary before screening. (2) The traditional mode of “screening single compound” could be improved to “screening single compound, drug combination and multicomponent interaction” due to the fact that herbal medicines work by integrative effects of multi-components rather than single effective constituents. Based on the two concepts, we established a novel strategy aiming to make screening easier and deeper. Using thrombin as the model enzyme, we firstly uncovered the minor lead compounds, potential drug combinations and multicomponent interactions in an herbal medicine of Dan-Qi pair, showing a significant advantage over previous methods. This strategy was expected to be a new and promising mode for investigation of herbal medicines.

Adulteration of Dietary Supplements by the Illegal Addition of Synthetic Drugs: A Review

In the last few years, the consumption of dietary supplements, especially those having plants as ingredients, has been increasing due to the common idea that they are natural products posing no risks to human health. In the European Union and the United States, dietary supplements are legally considered as foods/special category of foods, thus are not being submitted to any safety assessment prior to their commercialization. Among the issues that can affect safety, adulteration by the illegal addition of pharmaceutical substances or their analogs is of major concern since unscrupulous producers can falsify these products to provide for quick effects and to increase sales. This review discusses the various classes of synthetic drugs most frequently described as being illegally added to dietary supplements marketed for weight loss, muscle building/sport performance and sexual performance enhancement. Information regarding regulation and consumption is also presented. Finally, several conventional and advanced analytical techniques used to detect and identify different adulterants in dietary supplements and therefore also in foods, with particular emphasis on plant food supplements, are critically described. This review demonstrates that dietary supplement adulteration is an emerging food safety problem and that an effective control by food regulatory authorities is needed to safeguard consumers.

Application of Orbitrap-mass spectrometry to differentiate isomeric sildenafil- and thiosildenafil-like analogues used for the adulteration of dietary supplements

Two groups of isomeric phosphodiestrase-type 5 inhibitors (PDE-5), consisting of four sildenafil- and three thiosildenafil-like analogues, have been successfully differentiated using high-resolution MS/MS. The optimised MS/MS data obtained from each compound were used to build a database with the aid of mass processing software. Isomeric compounds with very close chromatographic separation like dimethylsildenafil and homosildenafil could be distinguished by their unique fingerprint fragment ions in the MS/MS database. All fragment ions were within the mass tolerance of 5 ppm. One case study using an adulterated dietary supplement is included to provide more insights into this application.

Isolation and structural characterization of a new tadalafil analog (2-hydroxyethylnortadalafil) found in a dietary supplement

A screen for known PDE-5 inhibitors in a dietary supplement product marketed for "enhanced sexual performance" detected a compound that structurally resembled tadalafil. The compound was isolated from the supplement matrix using high-performance liquid chromatography with ultraviolet detection (HPLC-UV) and a fraction collector, and was further characterized using nuclear magnetic resonance (NMR), liquid chromatography-mass spectrometry (LC-MS), as well as high-resolution accurate mass mass spectrometry (HRAM-MS). The analog had an accurate mass of m/z 420.15614 (error is 1.77235ppm) for the protonated species [M+H](+), corresponding to a molecular formula of C23H22N3O5. Mass spectral fragmentation data suggested that the modification occurred in place of the CH3 located on the pyrazinopyridoindole-1,4-dione of tadalafil. NMR was utilized to further elucidate the configuration of the substitution. The analysis indicated that the moiety is a CH2CH2OH, hydroxyethyl group. The new analog has been named 2-hydroxyethylnortadalafil.

Detection, identification and quantification by 1H NMR of adulterants in 150 herbal dietary supplements marketed for improving sexual performance

One hundred and fifty dietary supplements (DS) marketed to increase sexual performance were analyzed. All these formulations were claimed to contain only natural compounds, plant extracts and/or vitamins. (1)H NMR spectroscopy was used for detecting the presence of adulterants and for their identification and quantification. Mass spectrometry was used as a complementary method for confirming the chemical structures. 61% of DS were adulterated with phosphodiesterase-5 inhibitors (PDE-5i) (27% with the PDE-5i medicines sildenafil, tadalafil and vardenafil, and 34% with their structurally modified analogues). Among them, 64% contained only one PDE-5i and 36% mixtures of two, three and even four. The amounts of PDE-5i medicines were higher than the maximum recommended dose in 25% of DS tainted with these drugs. Additional 5.5% DS included other drugs for the treatment of sexual dysfunction (yohimbine, flibanserin, phentolamine, dehydroepiandrosterone or testosterone). Some DS (2.5%) contained products (osthole, icariin) extracted from plants known to improve sexual performance. Only 31% of the samples could be considered as true herbal/natural products. A follow-up over time of several DS revealed that manufacturers make changes in the chemical composition of the formulations. Lack of quality or consistent manufacture (contamination possibly due to inadequate cleaning of the manufacturing chain, presence of impurities or degradation products, various compositions of a given DS with the same batch number, inadequate labelling) indicated poor manufacturing practices. In conclusion, this paper demonstrates the power of (1)H NMR spectroscopy as a first-line method for the detection of adulterated herbal/natural DS and the need for more effective quality control of purported herbal DS.