Structural elucidation of a PDE-5 inhibitor detected as an adulterant in a health supplement

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.

Combined Effects of Oligopeptides Isolated from Panax ginseng C.A. Meyer and Ostrea gigas Thunberg on Sexual Function in Male Mice

Male sexual debility affects patients’ confidence and damages the relationship between the couples and thus affects the stability of the family. This study aimed to investigate the effects of oligopeptides isolated from ginseng and oyster (GOPs and OOPs), separately and in combination, on sexual function in male mice. In the first experiment, male mice were randomly divided into five groups: vehicle control group; whey protein (125.0 mg kg⁻¹) group; and GOPs 62.5, 125.0, and 250.0 mg kg⁻¹ groups. In the second experiment, male mice were randomly divided into five groups: vehicle control group, whey protein (160.0 mg kg⁻¹) group, and OOPs 80.0, 160.0, and 320.0 mg kg⁻¹ groups. In the third experiment, male mice were randomly divided into six groups: vehicle control group, whey protein (222.5 mg kg⁻¹) group, and GOPs + OOPs 62.5 + 160.0, 62.5 + 320.0, and 125.0 + 160.0, 125.0 + 320.0 mg kg⁻¹ groups. Test substances were given by gavage once a day for 30 days. The sexual behavior parameters, serum nitric oxide (NO), testosterone, cyclic guanosine monophosphate (cGMP), and phosphodiesterase-5 (PDE5) concentrations were detected. We found that GOPs at 250.0 mg kg⁻¹ improved male sexual behavior, NO, and testosterone content, whereas GOPs at 62.5 and 125.0 mg kg⁻¹ and OOPs at 80.0, 160, and 320 mg kg⁻¹ did not have significant effects. The combination of 62.5 mg kg⁻¹ GOPs + 160.0 mg kg⁻¹ OOPs and the combination of 125.0 mg kg⁻¹ GOPs + 320.0 mg kg⁻¹ OOPs improved male sexual behavior, serum NO, testosterone, and cGMP contents and decreased PDE5 content. The combination of 62.5 mg kg⁻¹ GOPs and 160.0 mg kg⁻¹ OOPs had the best effects among four combined groups. These results suggested that GOPs in combination with OOPs had the synergistic effects of enhancing male sexual function, probably via elevating serum testosterone, NO, and corpus cavernosum cGMP level and decreasing the corpus cavernosum PDE5 level. GOPs and OOPs could be novel natural agents for improving male sexual function.

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.

Spectroscopic and Spectrometric Methods Used for the Screening of Certain Herbal Food Supplements Suspected of Adulteration

Purpose: This study was carried out in order to find a reliable method for the fast detection of adulterated herbal food supplements with sexual enhancement claims. As some herbal products are advertised as "all natural", their "efficiency" is often increased by addition of active pharmaceutical ingredients such as PDE-5 inhibitors, which can be a real health threat for the consumer.

Methodes: Adulterants, potentially present in 50 herbal food supplements with sexual improvement claims, were detected using 2 spectroscopic methods - Raman and Fourier Transform Infrared - known for reliability, reproductibility, and an easy sample preparation. GC-MS technique was used to confirm the potential adulterants spectra.

Results: About 22% (11 out of 50 samples) of herbal food supplements with sexual enhancement claims analyzed by spectroscopic and spectrometric methods proved to be "enriched" with active pharmaceutical compounds such as: sildenafil and two of its analogues, tadalafil and phenolphthalein. The occurence of phenolphthalein could be the reason for the non-relevant results obtained by FTIR method in some samples. 91% of the adulterated herbal food supplements were originating from China.

Conclusion: The results of this screening highlighted the necessity for an accurate analysis of all alleged herbal aphrodisiacs on the Romanian market. This is a first such a screening analysis carried out on herbal food supplements with sexual enhancement claims.

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.

Evaluation of vibrational spectroscopic methods to identify and quantify multiple adulterants in herbal medicines

To counter the growth of herbal medicines adulterated with pharmaceuticals crossing borders, rapid, inexpensive and non-destructive analytical techniques, that can handle complex matrices, are required. Since mid-infrared (MIR), near infrared (NIR) and Raman spectroscopic techniques meet these criteria, their performance in identifying adulterants in seized weightloss herbal medicines is definitively determined. Initially a validated high pressure liquid chromatography methodology was used for reference identification and quantification of the adulterants sibutramine H2O·HCl, fenfluramine HCl and phenolphthalein. Of 38 products, only sibutramine and phenolphthalein were detected by HPLC. The spectroscopic measurements showed Raman was ill-suited due to sample burning and emission while NIR lacked adulterant selectivity. Conversely, MIR demonstrated apt identification performance, which manifested as spectrally meaningful separation based on the presence and type of adulterant during principal component analysis (test set validated). Partial least squares regression models were constructed from the MIR training sets for sibutramine and phenolphthalein - both models fitted the training set data well. Average test set prediction errors were 0.8% for sibutramine and 2.2% for phenolphthalein over the respective concentration ranges of 1.7-11.7% and 0.9-34.4%. MIR is apposite for the screening of anorectic and laxative adulterants and is the most viable technique for wider adulterant screening in herbal medicines.

Effectiveness of saikokaryukotsuboreito (herbal medicine) for antipsychotic-induced sexual dysfunction in male patients with schizophrenia: a description of two cases

Antipsychotics sometimes cause sexual dysfunction in people with schizophrenia. The authors report the effectiveness of Saikokaryukotsuboreito (Japanese traditional herbal medicine, Chai-Hu-Jia-Long-Gu-Mu-Li-Tang in Chinese) for antipsychotic-induced sexual dysfunction in two male patients with schizophrenia. The first patient was a 28-year-old man with schizophrenia who suffered erectile dysfunction induced by olanzapine 10 mg/day; the erectile dysfunction significantly improved following the treatment of Saikokaryukotsuboreito 7.5 g/day. The other case was a 43-year-old man with schizophrenia who was receiving fluphenazine decanoate at 50 mg/month and had difficulties in ejaculation; add-on of Saikokaryukotsuboreito 7.5 g/day recovered his ejaculatory function. There has been no report on the effectiveness of Japanese herbal medicine formulations for antipsychotic-induced sexual dysfunction. Although the effectiveness of Saikokaryukotsuboreito needs to be tested in systematic clinical trials, this herbal medicine may be a treatment option to consider for this annoying side effect.

Structural elucidation of a new sildenafil analogue using high-resolution Orbitrap mass spectrometry

RATIONALE

One new phosphodiesterase type 5 (PDE-V) inhibitor, propoxyphenyl homohydroxysildenafil (PP-HHS), has been isolated from one health supplement, and analyzed using high-resolution Orbitrap mass spectrometry. High-resolution mass spectrometry (HRMS) is useful to elucidate unknown substances at low concentrations.

METHODS

Two isolated compounds, propoxyphenyl thiohomohydroxysildenafil (PP-THHS) and propoxyphenyl homohydroxysildenafil (PP-HHS), were infused into the Thermo Fischer Scientific LTQ Orbitrap XL™ hybrid FTMS system at a flow rate of 3 μL per min. The high-resolution MS(2) spectra were acquired using different high-energy collision dissolution (HCD) mode; 40 V for PPT-HHS and 45 V for PP-HHS. The accurate mass measurement was assisted with the aid of Mass Frontier software, version 5.0.

RESULTS

The fragmentation pattern of PP-HHS in the MS(2) spectrum is very similar to that of PP-THHS except the product ions at m/z 519, 501, 325, 299 and 283 are less than PP-THHS by 16 m/z units. This is a result of the replacement of sulfur atom by oxygen at the thiolactam moiety. All the mass errors are below 5.0 ppm.

CONCLUSIONS

High-resolution Orbitrap mass spectrometry is an alternative method to determine unknown compounds like PDE-V inhibitor analogues unambiguously by analyzing the product ions at high mass accuracy. PP-HHS is an unapproved drug and no pharmacological study has been reported. Hence, it could be harmful to unknowing consumers with undesirable side effects.

Screening of synthetic PDE-5 inhibitors and their analogues as adulterants: analytical techniques and challenges

The popularity of phosphodiesterase type 5 (PDE-5) enzyme inhibitors for the treatment of erectile dysfunction has led to the increase in prevalence of illicit sexual performance enhancement products. PDE-5 inhibitors, namely sildenafil, tadalafil and vardenafil, and their unapproved designer analogues are being increasingly used as adulterants in the herbal products and health supplements marketed for sexual performance enhancement. To date, more than 50 unapproved analogues of prescription PDE-5 inhibitors were found as adulterants in the literature. To avoid detection of such adulteration by standard screening protocols, the perpetrators of such illegal products are investing time and resources to synthesize exotic analogues and devise novel means for adulteration. A comprehensive review of conventional and advance analytical techniques to detect and characterize the adulterants is presented. The rapid identification and structural elucidation of unknown analogues as adulterants is greatly enhanced by the wide myriad of analytical techniques employed, including high performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), liquid chromatography mass-spectrometry (LC-MS), nuclear magnetic resonance (NMR) spectroscopy, vibrational spectroscopy, liquid chromatography-Fourier transform ion cyclotron resonance-mass spectrometry (LC-FT-ICR-MS), liquid chromatograph-hybrid triple quadrupole linear ion trap mass spectrometer with information dependent acquisition, ultra high performance liquid chromatography-time of flight-mass spectrometry (UHPLC-TOF-MS), ion mobility spectroscopy (IMS) and immunoassay methods. The many challenges in detecting and characterizing such adulterants, and the need for concerted effort to curb adulteration in order to safe guard public safety and interest are discussed.

Evaluation of the residual solvent content of counterfeit tablets and capsules

A group of counterfeit samples of Viagra and Cialis were screened for their residual solvent content and compared to the content of the genuine products. It was observed that all counterfeit samples had higher residual solvent contents compared to the genuine products. A more diverse range of residual solvents was found as well as higher concentrations. In general these concentrations did not exceed the international imposed maximum limits. Only in a few samples the limits were exceeded. A Projection Pursuit analysis revealed clusters of samples with similar residual solvent content, possibly enabling some future perspectives in forensic research.

Rapid detection and identification of counterfeit and [corrected] adulterated products of synthetic phosphodiesterase type-5 inhibitors with an atmospheric solids analysis probe

The market success of the three approved synthetic phosphodiesterase type-5 (PDE-5) inhibitors for the treatment of erectile dysfunction has led to an explosion in counterfeit versions of these drugs. In parallel a large market has developed for herbal products claimed to be natural alternatives to these synthetic drugs. The herbal products are heavily advertised on the internet and are freely available to purchase without prescription. Furthermore, adulteration of these supposed natural medicines is a very common and serious phenomenon. Recent reports have shown that the adulteration has extended to the analogues of the three approved synthetic PDE-5 inhibitors. An Atmospheric Solids Analysis Probe (ASAP) was used for the direct analysis of the counterfeit pharmaceuticals and herbal products. Using the ASAP combined with time-of-flight mass spectrometry (TOF MS) it was possible to detect fraudulent counterfeit tablets. The physical appearance of the pills resembled the pills from the original manufacturer but contained the wrong active pharmaceutical ingredient (API). Detecting adulteration for five herbal supplements marketed as natural alternatives to PDE-5 inhibitors was also possible using the ASAP. Three types of adulteration were found in the five samples: adulteration with tadalafil or sildenafil, mixed adulteration (tadalafil and sildenafil), and adulteration with analogues of these drugs.

Isolation and structural elucidation of dapoxetine as an adulterant in a health supplement used for sexual performance enhancement

A health supplement used for sexual performance enhancement was sent to Health Sciences Authority of Singapore for testing. An unknown compound was detected and isolated and its structure was elucidated using NMR, high-resolution MS, ESI-MS/MS, UV and IR. The compound, dapoxetine, is reported to be a selective serotonin reuptake inhibitor under investigation for the treatment of premature ejaculation.