Isolation and identification of hydroxythiohomosildenafil in herbal dietary supplements sold as sexual performance enhancement products

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.

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.

Sildenafil 4.0-Integrated Synthetic Chemistry, Formulation and Analytical Strategies Effecting Immense Therapeutic and Societal Impact in the Fourth Industrial Era

Sildenafil is a potent selective, reversible inhibitor of phosphodiesterase type 5 (PDE5) approved for the treatment of erectile dysfunction and pulmonary arterial hypertension. Whilst twenty years have passed since its original approval by the US Food and Drug Administration (USFDA), sildenafil enters the fourth industrial era catalyzing the treatment advances against erectile dysfunction and pulmonary hypertension. The plethora of detailed clinical data accumulated and the two sildenafil analogues marketed, namely tadalafil and vardenafil, signify the relevant therapeutic and commercial achievements. The pharmacokinetic and pharmacodynamic behavior of the drug appears complex, interdependent and of critical importance whereas the treatment of special population cohorts is considered. The diversity of the available formulation strategies and their compatible administration routes, extend from tablets to bolus suspensions and from per os to intravenous, respectively, inheriting the associated strengths and weaknesses. In this comprehensive review, we attempt to elucidate the multi-disciplinary elements spanning the knowledge fields of chemical synthesis, physicochemical properties, pharmacology, clinical applications, biopharmaceutical profile, formulation approaches for different routes of administration and analytical strategies, currently employed to guide the development of sildenafil-based compositions.

Suspected-target and non-targeted screenings of phosphodiesterase 5 inhibitors in herbal remedies using liquid chromatography-quadrupole time-of-flight-mass spectrometry

The lucrative market of herbal remedies spurs rampant adulteration, particularly with pharmaceutical drugs and their unapproved analogues. A comprehensive screening strategy is, therefore, warranted to detect these adulterants and, accordingly, to safeguard public health. This study uses the data-dependent acquisition of liquid chromatography-quadrupole time-of-flight-mass spectrometry (LC-QTOF-MS) to screen phosphodiesterase 5 (PDE5) inhibitors in herbal remedies using suspected-target and non-targeted strategies. For the suspected-target screening, we used a library comprising 95 PDE5 inhibitors. For the non-targeted screening, we adopted top-down and bottom-up approaches to flag novel PDE5 inhibitor analogues based on common fragmentation patterns. LC-QTOF-MS was optimised and validated for capsule and tablet dosage forms using 23 target analytes, selected to represent different groups of PDE5 inhibitors. The method exhibited excellent specificity and linearity with limit of detection and limit of quantification of <40 and 80 ng/mL, respectively. The accuracy ranged from 79.0% to 124.7% with a precision of <14.9% relative standard deviation. The modified, quick, easy, cheap, effective, rugged, and safe extraction provided insignificant matrix effect within -9.1%-8.0% and satisfactory extraction recovery of 71.5%-105.8%. These strategies were used to screen 52 herbal remedy samples that claimed to enhance male sexual performance. The suspected-target screening resulted in 33 positive samples, revealing 10 target analytes and 2 suspected analytes. Systematic MS and tandem MS interrogations using the non-targeted screening returned insignificant signals, indicating the absence of potentially novel analogues. The target analytes were quantified from 0.03 to 121.31 mg per dose of each sample. The proposed strategies ensure that all PDE5 inhibitors are comprehensively screened, providing a useful tool to curb the widespread adulteration of herbal remedies.

Metabolites of Dietary Acteoside: Profiles, Isolation, Identification, and Hepatoprotective Capacities

In recent years, cistanche tea has been increasingly used as a major herbal supplement in functional drinks, and it has attracted a growing number of consumers because of its excellent tonic effects and medicinal properties. Acteoside (ACT), which is the principal bioactive component of Chinese cistanche tea, possesses various pharmacological effects. This study profiled, isolated, identified, and investigated the hepatoprotective capacities of metabolites in rat urine after the administration of ACT. Eleven metabolites, including one new compound (M8), were obtained and identified by nuclear magnetic resonance (NMR) spectroscopy for the first time. Compared with native ACT, ACT metabolites such as hydroxytyrosol (HT), 3-hydroxyphenylpropionic acid (3-HPP), and caffeic acid (CA) exhibited higher hepatoprotective activities by regulating oxidative stress, lipid peroxidation, and inflammatory responses in a GalN/LPS-induced-acute-hepatic-injury mouse model. The HT treatment markedly reduced the levels of TNF-α to 280 ± 14.3 ng/L compared with the model group (429 ± 9.20 ng/L, p < 0.01). The results obtained indicated that cistanche tea could be developed as a functional drink for the prevention of hepatic injuries and that ACT metabolites could be responsible for the potent hepatoprotective activity as well as the other therapeutic 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.

Dietary supplements on the domestic market adulterated with sildenafil and tadalafil

Az étrend-kiegészítők gyártását és forgalmazását nem garantálják a gyógyszerszabályozáshoz hasonlóan szigorú jogszabályok. Az elmúlt években a termékcsoport tagjainak száma meredeken emelkedett, és ezzel párhuzamosan szaporodtak a készítmények reklámozásával, ajánlásával és minőségével kapcsolatos visszaélések. A termékek hamisításának egyik gyakori módja a szintetikus gyógyszerhatóanyagok jelölés nélküli felhasználása növényi eredetű készítményekben. Vizsgálatunkban 10, hazánkban forgalomban lévő, potenciafokozóként (vagy ezt a hatást sugallva) reklámozott étrend-kiegészítőt vontunk kémiai elemzés alá. Hat termékben szildenafil és/vagy tadalafil vagy a vegyületek analógjai voltak kimutathatóak. Eredményeink felhívják a figyelmet arra, hogy a rossz minőségű, hamisított étrend-kiegészítők valós egészségi kockázatot jelentenek a fogyasztók számára. Orv. Hetil., 2010,43,1783–1789.

Assessment of herbal medicinal products: challenges, and opportunities to increase the knowledge base for safety assessment

Although herbal medicinal products (HMP) have been perceived by the public as relatively low risk, there has been more recognition of the potential risks associated with this type of product as the use of HMPs increases. Potential harm can occur via inherent toxicity of herbs, as well as from contamination, adulteration, plant misidentification, and interactions with other herbal products or pharmaceutical drugs. Regulatory safety assessment for HMPs relies on both the assessment of cases of adverse reactions and the review of published toxicity information. However, the conduct of such an integrated investigation has many challenges in terms of the quantity and quality of information. Adverse reactions are under-reported, product quality may be less than ideal, herbs have a complex composition and there is lack of information on the toxicity of medicinal herbs or their constituents. Nevertheless, opportunities exist to capitalise on newer information to increase the current body of scientific evidence. Novel sources of information are reviewed, such as the use of poison control data to augment adverse reaction information from national pharmacovigilance databases, and the use of more recent toxicological assessment techniques such as predictive toxicology and omics. The integration of all available information can reduce the uncertainty in decision making with respect to herbal medicinal products. The example of Aristolochia and aristolochic acids is used to highlight the challenges related to safety assessment, and the opportunities that exist to more accurately elucidate the toxicity of herbal medicines.