Isolation and identification of a new sildenafil analogue adulterated in energy drink: Propoxyphenyl sildenafil

Kee C., Ge X., Koh H., Low M.

Two new phosphodiesterase-5 inhibitors (PDE-5) which consist of one sildenafil analogue and one thiosildenafil analogue have been found in heath supplements. The structural properties of these analogues have been elucidated by NMR, high resolution MS, MS(2), UV and IR spectroscopy. The sildenafil analogue is very similar to aildenafil and the thiosildenafil analogue is similar to thioaildenafil, except the ethoxy group bonded to phenyl ring is replaced by a propoxy group. Hence, the sildenafil analogue is named as propoxyphenyl aildenafil or propoxyphenyl methisosildenafil and the thiosildenafil analogue as propoxyphenyl thioaildenafil or propoxyphenyl thiomethisosildenafil.

Venhuis B.J., de Kaste D.

The scale at which erectile dysfunction (ED) medicines are obtained outside of the official health system rivals and possibly exceeds legitimate sales. According to literature a high-risk segment of this market is occupied by adulterated food supplements. The principle adulterants identified were structural analogues of the registered ED drugs sildenafil, tadalafil, and vardenafil. Currently, at least 46 different analogues have been reported and still more are expected. The intellectual origin of analogues was found in patent literature which described the drug discovery process. Patent literature offers a flexible approach to synthesize hundreds of analogues. Most of the analogues currently known had long been disclosed in patent literature. Screening for (new) analogues is best carried out by using advanced LC-MS/MS techniques that focus on marker fragment ions. Analogues are experimental drugs in essence because most have no known efficacy or safety profile. Their use in seemingly harmless food supplements is expected to cause serious adverse effects. However, few reports have emerged in literature on actual harm. Considering the exposure to analogues and their adverse effects being unknown a gross underreporting of complaints is expected.

Balayssac S., Gilard V., Zedde C., Martino R., Malet-Martino M.

Nine herbal dietary supplements intended to be beverages for enhancing sexual performance were analyzed before their possible launch on the market. Four of them contained a sildenafil analog reported for the first time as an adulterant. After isolation and characterization using NMR, MS, IR and UV, this analog was named propoxyphenyl-thiohydroxyhomosildenafil as the ethoxy chain on the phenyl ring of the already known analog thiohydroxyhomosildenafil was replaced by a propoxy moiety. One formulation was tainted with thiosildenafil, another unapproved PDE-5 inhibitor. Sildenafil along with the natural alkaloid tetrahydropalmatine that has no documented effect for enhancing erectile dysfunction were identified in two formulations. Another formulation was adulterated with phentolamine, a drug that is not approved for boosting male sexual performance when taken orally. The last formulation containing osthole, a bioactive natural coumarine improving sexual dysfunction, is most probably truly natural.

Vaysse J., Gilard V., Balayssac S., Zedde C., Martino R., Malet-Martino M.

iErect, a new dietary supplement marketed as "100% natural" and sold over the Internet, was analyzed. It contains thiosildenafil, a sildenafil analogue already reported as an adulterant in herbal formulations, and a new compound whose structure was elucidated after isolation using NMR, MS and IR. It was named depiperazinothiosildenafil as it results from the hydrolytic cleavage of the S-N bond of the sulfonamide group of thiosildenafil. A capsule of iErect contains a very high amount (≈220mg) of thiosildenafil and ≈30mg of depiperazinothiosildenafil, which places consumers at risk for potentially serious side-effects.

Lee H., Kim C.S., Jang Y.M., Kwon S.W., Lee B.

MEGATON, a dietary supplement, was analyzed in order to detect PDE-5 inhibitors and their analogues. A new analogue of vardenafil could be detected by high-performance liquid chromatography (HPLC) analysis with a photodiode array detector (PDA). This compound was compared with sildenafil, tadalafil, and vardenafil as well as their structurally modified analogues such as hongdenafil and homosildenafil. The structure of this compound was elucidated by mass spectrometry (MS), infrared (IR) spectroscopy and one- and two-dimensional nuclear magnetic resonance (NMR) spectroscopy. When compared with vardenafil to verify the structural difference, this compound had an acetyl group instead of a sulfonyl group in the pyrazolopyrimidine portion without any substitution in the piperazine ring of the molecule. This compound was identified as 2-(2-ethoxy-5-(2-(4-ethylpiperazin-1-yl)acetyl)phenyl)-5-methyl-7-propyl-imidazo(5,1-f)-(1,2,4)triazin-4(3H)-one, which is also called acetylvardenafil.

Kesting J.R., Huang J., Sørensen D.

Based on anecdotal evidence of anti-hypertensive effect of Gold Nine Soft Capsules, an in vivo study of this complex Chinese "herbal-based" medicine was initiated. Dosage of the content of Gold Nine capsules in spontaneous hypertensive rats showed a remarkably good effect. This led to further investigation of the components of the preparation and eventual identification of three known anti-hypertensive drugs; amlodipine, indapamide and valsartan, which were not declared on the label. Compounds were rapidly identified using LC-HRMS and LC-MS-SPE/NMR, quantified by HPLC, and the in vivo activity of a combination of commercially purchased standards was shown to be equivalent to that of the capsule content. Adulteration of herbal remedies and dietary supplements with synthetic drugs is an increasing problem that may lead to serious adverse effects. LC-MS-SPE/NMR as a method for the rapid identification of such adulterants is highlighted in this case study.

Maddox P.T., Saunders J., Chandrasekhar S.S.

Zou P., Hou P., Oh S.S., Chong Y.M., Bloodworth B.C., Low M., Koh H.

Two unknown compounds are detected and isolated from health supplements for the enhancement of sexual function. The structures of the unknown compounds are elucidated using high-resolution MS, ESI-MS/MS, NMR, UV and IR. One compound is identified as an analogue of sildenafil in which the oxygen atom is substituted with a sulfur atom in the pyrazolopyrimidine moiety, and an ethyl group instead of a methyl group is attached to the piperazinyl nitrogen. Hence, this compound is named thiohomosildenafil. Another compound is also a sildenafil analogue in which the oxygen atom is substituted with a sulfur atom in the pyrazolopyrimidine moiety. This compound is named thiosildenafil. Both the two compounds are first detected in health supplements. The UV, IR and completely assigned NMR data of thiohomosildenafil and thiosildenafil are first reported.

Pissarnitski D.

The role of phosphodiesterase type 5 (PDE5) in the mechanism of male erection has been well understood, and several drugs inhibiting this enzyme are being used for the treatment of erectile dysfunction (ED). Discovery of inhibitors with improved selectivity versus other PDE isozymes could lead to drugs with improved safety profile. Achievement of selectivity versus PDE6, co-inhibition of which results in disturbances of color perception, remains the most challenging aspect of current drug discovery programs. The present review describes several case studies, where significant (>100 fold) selectivity versus PDE6 has been attained via investigation of structure–activity relationships (SAR). Special attention is given to the chemical routes leading to novel chemotypes and allowing efficient exploration of their SAR's. Strategies for attaining inhibitor selectivity discussed below may be applicable for other drug discovery programs. © 2005 Wiley Periodicals, Inc. Med Res Rev

Pomeranz H.D., Bhavsar A.R.

Seven patients, aged between 50 and 69 years, had typical features of nonarteritic anterior ischemic optic neuropathy (NAION) within 36 hours after ingestion of sildenafil citrate (Viagra) for erectile dysfunction. Six patients had vision loss within 24 hours after use of the agent. Final visual acuity in the affected eye ranged from 20/20 to light perception. Both eyes were affected in one individual. All affected individuals had pre-existing hypertension, diabetes, elevated cholesterol, or hyperlipidemia. Seven similar cases have been previously reported. Sildenafil may provoke NAION in individuals with an arteriosclerotic risk profile.

Kloner R.A.

Received May 17, 2004; revision received June 22, 2004; accepted June 22, 2004. Within the last year, 2 new phosphodiesterase-5 (PDE5) inhibitors have been approved by the US Food and Drug Administration (FDA) for the treatment of erectile dysfunction (ED). Currently, sildenafil (Viagra), vardenafil (Levitra), and tadalafil (Cialis) are on the market. These agents have been shown to be effective in a broad population of men with ED, including patients with vascular disease, coronary artery disease, hypertension, and diabetes.1–5 Because the enzyme that they inhibit, PDE-5, is found in smooth muscle cells of the systemic arteries and veins throughout the body, these agents have mild vasodilator effects and thus, have the potential to impact the cardiovascular system.6 This fact is especially important for the patient with ED, because risk factors for ED include many of the same risk factors that are associated with coronary artery disease: lipid abnormalities, hypertension, smoking, diabetes, and lack of physical exercise.7,8 Because erection is a vascular event, endothelial dysfunction may inhibit it.9 Endothelial dysfunction, an early component of atherosclerosis, is rarely confined to the arteries supplying blood to the penis but more likely occurs throughout the vascular bed. Kaiser et al10 studied 30 men with ED and observed that brachial artery flow–mediated vasodilation and nitroglycerin-mediated vasodilation were reduced in these patients compared with men without ED. Thus, ED may be an early marker of vascular disease.10 Patients with frank coronary artery disease, known to be associated with endothelial dysfunction, and frank atherosclerosis often have ED, as we recently observed in 1 study, in which three fourths of the men with chronic stable angina also reported some degree of ED.11 Hence, the vasodilator effect of these PDE5 agents should be taken into consideration for the cardiac patient, both as …

Blok-Tip L., Zomer B., Bakker F., Hartog K.D., Hamzink M., ten Hove J., Vredenbregt M., de Kaste * D.

The structure of unknown compounds present in herbal products was elucidated using liquid chromatography-electrospray ionization-mass spectrometry, direct-infusion electrospray ionization-mass spectrometry, and nuclear magnetic resonance. Compounds 1-3 were identified as sildenafil analogues, 1 bearing an N-ethylpiperazine moiety instead of an N-methylpiperazine, and an acetyl group instead of the sulfonyl group, named acetildenafil, 2 bearing an N-ethylpiperazine moiety instead of an N-methylpiperazine (homosildenafil), and 3 bearing an N-hydroxylethylpiperazine moiety instead of an N-methylpiperazine, named hydroxyhomosildenafil. When analysing products marketed for penile erectile dysfunction or marketed as aphrodisiacs, attention should be given to the possible presence of these components.

Shin M.-., Hong M.-., Kim W.-., Lee Y.-., Jeoung Y.-.

A new analogue of sildenafil was discovered to have been added illegally to a functional food marketed for penile erectile dysfunction. The structure of the analogue was established by various NMR spectroscopic techniques (including DEPT, COSY, TOCSY, HMQC, HMBC). Because of the addition of a methylene group to sildenafil, the main ingredient of Viagra(R), it was given the name homosildenafil, and this has never been reported previously. An analytical method using HPLC was proposed. Homosildenafil was added as a new inspection item and other foods have since been discovered to contain it.

Üstündağ İ., Caglayan M.O.

Tadalafil is one of the selective phosphodiesterase type 5 inhibitors (PDE5) and serves as the active compound in drugs used for the treatment of erectile dysfunction. These PDE5 inhibitors are prescribed under medical supervision. However, cases of adulteration of dietary supplements with PDE5 inhibitors or their unapproved analogs have been reported worldwide. The presence of the PDE5 inhibitors in such supplements poses a serious health risk to consumers, particularly when combined with certain nitrate-containing drugs, as their toxic effects have not been thoroughly assessed and may result in unpredictable adverse reactions. Therefore, it is crucial to detect adulteration in these dietary supplements. However, current methods for PDE5 inhibitor detection rely on time-consuming and expensive analytical techniques, although they are sensitive. In this study, we propose an aptasensor based on ellipsometry for the detection of PDE5 inhibitors. To enhance the detection specificity for PDE5 inhibitors, we designed an aptamer with a hydrophobic pocket that incorporates a guanine base-rich region and a three-way junction. This design is particularly effective considering the poor aqueous solubility of PDE5 inhibitors. Preliminary results demonstrate that tadalafil detection in various media can be achieved within the range of 1–2000 ng/mL. The limit of detection for the active compound of tadalafil is as low as 1.82 ng/mL.

Kee C., Ge X., Low M., Gilard V., Malet-Martino M.

Li G., Pan Q., Zhang C., Wang J., Peng C., Wang Z.

Some phosphodiesterase type-5 (PDE5) inhibitors are active ingredients of prescription drugs that are widely used in the treatment of erectile dysfunction (ED). Recently, a large number of substances with this activity have been developed. Illegal addition of PDE5 inhibitors to foods could lead to cardiovascular diseases and even death, which poses a serious threat to food safety, therefore an on-site rapid screening method is urgently needed. Herein, a host functionalized bimetallic nanoclusters, CD/Au Ag NCs, were synthesized through self-assembly of 6-Aza-2-thiothymine gold nanoclusters (ATT-Au NCs), Arginine silver nanoclusters (Arg-Ag NCs) and carboxymethyl β-cyclodextrin (β-CMCD). The introduction of Rhodamine 6G (R6G) could quench the fluorescence of CD/Au Ag NCs based on the inner filter effect (IFE) and fluorescence resonance energy transfer effect (FRET). Importantly, it was discovered that several PDE5 inhibitors exhibited a higher binding affinity to β-CMCD and could displace R6G binding with CD cavity, which disrupted the fluorescence quenching effects and resulted in the fluorescence recovery of CD/Au Ag NCs. This fluorescence turn-on signal could be utilized for the detection of PDE5 inhibitors. At present, emerging PDE5 inhibitor analogues pose a great challenge to food safety due to their unknown efficacy and safety. The proposed method holds the advantages of high sensitivity, simple probe synthesis, easy operation, and simultaneous detection of multiple PDE5 inhibitors. Meanwhile, the successful application in functional food sample demonstrated its high application potential in multiple PDE5 inhibitors screening.

Oller-Ruiz A., Campillo N., Fenoll J., Hernández-Córdoba M., Viñas P.

A dispersive magnetic solid-phase extraction (DMPSE) procedure has been developed to preconcentrate four synthetic phosphodiesterase type 5 (PDE-5) inhibitors (sildenafil, desmethylsildenafil, vardenafil and tadalafil) from different samples (human hair, energy drinks, lubricating gels and dietary supplements). The target compounds were isolated from the solid samples by solid-liquid extraction in basic aqueous medium and the extract was submitted to DMSPE using multiwalled carbon nanotubes/Fe3O4@polypyrrole (MWCNTs/Fe3O4@PPy). For this, 20 mg of the magnetic nanocomposite was added to 30 mL of sample solution/extract and vortexed for 10 min before proceeding to the desorption step using 1 mL of methanol. Analysis was carried out by liquid chromatography with tandem mass spectrometry using electrospray ionization and a triple quadrupole mass analyzer (LC-ESI-QqQ-MS/MS). Matrix-matched calibration was applied for quantification. Limits of detection ranged between 0.01 and 0.22 ng mL−1 for energy drinks and between 0.25 and 7.5 ng g−1 for hair, lubricating gels, and dietary supplements. Relative standard deviations in the 4.3–12.2% (n = 10) were obtained for repeatability studies. The trueness of the proposed method was studied by fortifying the samples at two concentration levels and recoveries in the 85–112% range were obtained. None of the PDE-5 inhibitors studied were detected in real samples.

He F., Yang J., Zou T., Xu Z., Tian Y., Sun W., Wang H., Sun Y., Lei H., Chen Z., Liu J., Tan X., Shen Y.

In the last few years, sildenafil and its analogues have emerged as an illegal ingredient in health food and products, causing illness and death. To address this problem, herein, a gold nanoparticle-based immunochromatographic assay for simultaneous detection sildenafil and its analogues was developed by using just one monoclonal antibody. This method can realize qualitative and quantitative analysis of sildenafil and its analogues with a detection range (IC 20 -IC 80 ) of 0.12–28.05 ng mL −1 , the IC 50 was 0.31–8.45 ng mL −1 and the cut-off value was 5.0–80.0 ng mL −1 . Meanwhile, this method could also accomplish semi-quantitative analysis of vardenafil with a cut-off value of 0.625 ng mL −1 . The detection can be finished in 6 min and showed no cross-reactivity with avanafil and tadalafil. The recoveries of spiked samples ranged from 70.5 to 118.9% with a coefficient variation less than 15%, which confirmed the assay was sensitive, accurate and adapted to the rapid determination of sildenafil and its analogues. Sildenafil adulteration.[ ] • A sensitive GNPs ICA for 10 sildenafil adulterants was developed based on one broad-spectrum mAb. • The comparison with reported antibodies were also made by molecular simulation to evaluate the better performance. • The test results of real samples have good correlation with UPLC-MS/MS.

Wang K., Zeng H., Zhang Y., Xie X., Yue Z., Zhang W., Fu C., Luo L., Fan H.

A novel method for hierarchical screening of illegal adulterants in Fur seal ginseng pills products was developed by multi-dimensional fingerprint profiling analysis. Fingerprint feature of the samples was acquired by high-performance liquid chromatography analysis of 11 batches of samples with diode array detector and fluorescence detector, and then potential illegal adulterants including phosphodiesterase type-5 inhibitors, androgens, α receptor antagonists and yohimbine, were further separated at multiple wavelengths to reduce or remove interferences from sample matrix for highlight their chromatographic characteristics. Accordingly, a hierarchical screening strategy was designed by first-order and second-order fingerprints combined with spectral examination to achieve high accuracy and reliability. The method was successfully applied to screening of illegal adulterants in real samples, and it also exhibited good quantification performance through validation tests. From 16 batches of samples, three suspected samples were confirmed to be positive, containing 9.37μg/g of testosterone, 18.8 μg/g of tadalafil, and 48.5 μg/g of sildenafil, respectively. The recoveries and relative standard deviations were in the range of 83.6-103.1% and 4.2-6.8%, respectively. The proposed method provided a simple, efficient and promising alternative to monitoring functional foods.

He F., Zou T., Yang J., Wang H., Deng L., Tian Y., Xu Z., Sun Y., Lei H., Tan X., Shen Y.

ABSTRACTIn this work, a rapid, convenient and sensitive Au nanoparticle-based immunochromatographic sensor (AuNPs-ICS) for simultaneous detection of various tadalafil adulterants in health food was established for the first time, based on one high affinity and broad-spectrum antibody through skeleton-specific hapten design according to the common structure of tadalafil drugs. This immunochromatographic sensor was developed by the polyclonal antibody conjugated with AuNPs and the IC50 was 10.04 ng mL−1 for tadalafil and 9.55, 11.46, 17.01 ng mL−1 for amino tadalafil, acetamino tadalafil and nortadalafil, respectively. The limit of detection results could be obtained visually by naked eyes for and computationally by the hand-held immunochromatography reader. The sensor could specially detect Tadalafil and its analogs within 10 min in health food samples, and the close correlation with UPLC-MS/MS method showed the sensor was accurate and reliable, which could apply to on site detection Tadalafil and its anal...

Kee C., Ge X., Gilard V., Malet-Martino M., Low M.

To date, there are 80 synthetic PDE-5i found as adulterants in dietary supplements. Analogues of sildenafil remain as the top list with 50 (62%) and are followed by analogues of tadalafil, 21 (26%), analogues of vardenafil, 7 (9%) and others, 2 (3%). The sildenafil group can be sub-categorized into sulphonamide-bonded (24, 48%), acetyl-bonded (11, 22%), carbonyl or thiocarbonyl-bonded (8, 16%) and other types (7, 14%) based on the functional group linked to pyrazolopyrimidine-one moieties. Meanwhile, analogues of tadalafil have become popularly found as adulterants in dietary supplements like beverages and herbal extracts from 2015 to 2016. The uptrend has been observed with the increase in number and complexity with more trans-oriented and dimerized tadalafil analogues being reported. Interestingly, there is no much increase for analogues of vardenafil. About two thirds of analogues have been reported from the Asian countries (67%), followed by Europe (22%) and North America (11%). South Korea and Singapore have reported the most number of analogues with a total number of 40 (50%). One plausible contributing factor to this trend is the convenient purchase of sexual enhancement dietary supplements, especially the on-line purchase. In terms of analytical methodologies, high performance liquid chromatography (HPLC) hyphenated to ultra-violet (UV) and/or mass spectrometry (MS) detection have been preferred in the screening analysis, i.e. 70 out of 77 compounds have been analysed by HPLC-UV. In addition, the electrospray ionization multistage fragmentation experiments (ESI-MSn) for acquiring low- and high-resolution mass spectra have been successfully applied to detect and quantify PDE-5i in adulterated products simultaneously. Nuclear magnetic resonance (NMR) is another important technique in the structural elucidation of novel analogues.

Sakamoto M., Suzuki J., Saito Y., Shimizu S., Kobayashi K., Nagashima M., Moriyasu T., Fukaya H., Saito K.

Two analogs of sildenafil (compounds 1 and 2) were detected in three powder products acquired from online drug markets during an LC-UV-MS analysis of psychotropic drugs. Their structures were established by high-resolution mass spectrometry and NMR spectroscopy. Compound 1 was identified as 5-(5-(3,5-dimethylpiperazine-1-carbonothioyl)-2-ethoxyphenyl)-1-methyl-3-propyl-1H-pyrazolo[4,3-d]pyrimidine-7(6H)-thione and named dimethyldithiodenafil. Compound 2 was identified as 5-(5-(3,5-dimethylpiperazine-1-carbonothioyl)-2-ethoxyphenyl)-1-methyl-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-7(6H)-one and named dimethylthiocarbodenafil. Compound 1 was subjected to the phosphodiesterase assay (IC50=0.20nM). The three powder products were found to contain 12-19mg of dimethyldithiodenafil and 1.4-3.9mg of dimethylthiocarbodenafil per tube.

Park H., Lee J., Kim J.Y., Hong J., Oh H.B.

A chemometric model, which utilizes quantitative structure–retention relationships, has been developed for predicting liquid chromatography retention times (RTs) of 41 erectile dysfunction (ED) dru...

Satheeshkumar N., Paul D., Lingesh A.

An ever increasing global demand for herbal-based medicines in recent years has resulted in a serious public concern over its quality and safety. The consumption of adulterated herbal products can lead to unexpected and unpredictable pharmacological responses in the human body and various health-related risks. Adulteration of herbal products is a global concern and poses a major challenge for analytical laboratories to detect and characterize them. Liquid chromatography coupled with mass spectrometry (LC–MS) is widely used for screening of adulterants, mainly due to their high selectivity and sensitivity, which is crucial for analyzing complex natural product samples. The present article consists of an overview of drug adulteration and evaluation of herbal products with a special reference to the approaches in adulterant detection and regulatory perspectives to control such malpractices. Also, adulteration in slimming phytotherapeutic formulations, PDE-5 inhibitors in herbal formulations has been discussed.

Ge X., Kee C.-., Zeng Y., Low M.-.

Custers D., Krakowska B., De Beer J.O., Courselle P., Daszykowski M., Apers S., Deconinck E.

Counterfeit medicines are a global threat to public health. High amounts enter the European market, which is why characterization of these products is a very important issue. In this study, a high-performance liquid chromatography–photodiode array (HPLC-PDA) and high-performance liquid chromatography–mass spectrometry (HPLC-MS) method were developed for the analysis of genuine Viagra®, generic products of Viagra®, and counterfeit samples in order to obtain different types of fingerprints. These data were included in the chemometric data analysis, aiming to test whether PDA and MS are complementary detection techniques. The MS data comprise both MS1 and MS2 fingerprints; the PDA data consist of fingerprints measured at three different wavelengths, i.e., 254, 270, and 290 nm, and all possible combinations of these wavelengths. First, it was verified if both groups of fingerprints can discriminate between genuine, generic, and counterfeit medicines separately; next, it was studied if the obtained results could be ameliorated by combining both fingerprint types. This data analysis showed that MS1 does not provide suitable classification models since several genuines and generics are classified as counterfeits and vice versa. However, when analyzing the MS1_MS2 data in combination with partial least squares-discriminant analysis (PLS-DA), a perfect discrimination was obtained. When only using data measured at 254 nm, good classification models can be obtained by k nearest neighbors (kNN) and soft independent modelling of class analogy (SIMCA), which might be interesting for the characterization of counterfeit drugs in developing countries. However, in general, the combination of PDA and MS data (254 nm_MS1) is preferred due to less classification errors between the genuines/generics and counterfeits compared to PDA and MS data separately.

Jeong J.H., Lee J.H., Kim H.J., Park H.J., Hwang I.S., Han K.M., Yoon C., Cho S., Kim W.S.

A number of 188 food and dietary supplement samples were collected from 2009 to the first half of 2013 in Korean online and offline stores. A method to identify phosphodiesterase-5 (PDE-5) inhibitors and their analogues using liquid chromatography-electrospray ionisation-mass spectrometry/mass spectrometry (LC-ESI-MS/MS) was validated. Limit of detection and limit of quantitation of liquid-type and solid-type negative samples ranged from 0.05 to 3.33 ng/mL or ng/g and from 0.15 to 10.00 ng/mL or ng/g, respectively. Recoveries ranged from 83% to 112%. Nineteen PDE-5 inhibitors and their analogues were detected, with tadalafil group compounds being the most frequently observed (53.0%), followed by the sildenafil group (42.5%). Tadalafil concentrations ranged from 0.08 to 138.69 mg/g. Compounds were most frequently detected in capsules (in 40 of 80 adulterated samples). To protect public health and food safety, appropriate monitoring of PDE-5 inhibitors and their analogues in foods and dietary supplements is recommended.

Xu Y., Kee C., Ge X., Low M., Koh H.

A tadalafil analogue was detected for the first time during the screening of a health supplement for undeclared sexual enhancement drugs. The compound had been isolated and purified by preparative high-pressure liquid chromatography (HPLC). Its chemical structure was elucidated using high-resolution mass spectrometry (HRMS), electrospray ionization tandem mass spectrometry (ESI-MS/MS) and nuclear magnetic resonance (NMR) spectroscopy. The compound had a protonated molecular ion at m/z 444 with a chemical formula of C26H25N3O4. The data obtained from the MS analysis of the compound suggested that the N-methyl group on the piperazinedione moiety of tadalafil was substituted with a -C5H9 group. Analysis using NMR was performed and the -C5H9 group was characterized as a cyclopentyl moiety. The analogue was named N-cyclopentyl nortadalafil.