Identification of a new tadalafil analogue found in a dietary 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.

Isolation and characterization of a novel tadalafil analogue adulterant, N-cyclohexyl nortadalafil, in a dietary supplement

A novel tadalafil analogue was detected during routine screening of dietary supplements suspected to be adulterated with an erectile dysfunction drug(s) by using ultra-high-performance liquid chromatography coupled to Quadrupole-Exactive Orbitrap mass spectrometry (UPLC‑Q‑Exactive Orbitrap/MS). The MS² spectrum of the compound was highly similar to that of tadalafil within the range of < 300 m/z. The UV spectrum of the compound was almost identical to that of tadalafil. The analogue was purified by semi-preparative HPLC and structurally elucidated by FT-IR, MS and NMR analysis. The analogue was finally determined as N-cyclohexyl nortadalafil, featuring the cyclohexyl group instead of the N-methyl group on the piperazinedione ring of tadalafil.

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.

Suspected Adulteration of Commercial Kratom Products with 7-Hydroxymitragynine

INTRODUCTION

Kratom (Mitragyna speciosa), a plant native to Southeast Asia, has been used for centuries for its stimulant and opium-like effects. Mitragynine and 7-hydroxymitragynine, exclusive to M. speciosa, are the alkaloids primary responsible for Kratom's biologic and psychoactive profile, and likely contribute to its problematic use. We purchased several commercially available Kratom analogs for analysis and through our results, present evidence of probable adulteration with the highly potent and addictive plant alkaloid, 7-hydroxymitragynine.

METHODS

A simple and sensitive LC-MS/MS method was developed for simultaneous quantification of mitragynine and 7-hydroxymitragynine in methanol extract of marketed Kratom supplements.

RESULTS

We found multiple commercial Kratom products to have concentrations of 7-hydroxymitragynine that are substantially higher than those found in raw M. speciosa leaves.

CONCLUSIONS

We have found multiple packaged commercial Kratom products likely to contain artificially elevated concentrations of 7-hydroxymitragynine, the alkaloid responsible for M. speciosa's concerning mechanistic and side effect profile. This study describes a unique form of product adulteration, which stresses the importance of increased dietary supplement oversight of Kratom-containing supplements.

Determination of phosphodiesterase type V inhibitors in wastewater by direct injection followed by liquid chromatography coupled to tandem mass spectrometry

A simple, fast and reliable analytical method for the determination of phosphodiesterase type V inhibitors in wastewater was developed and validated. The method was based on direct injection followed by liquid chromatography coupled to tandem mass spectrometry with triple quadrupole as mass analyzer. Transformation products and analogues were included in the target list besides the three active pharmaceutical ingredients (sildenafil, vardenafil and tadalafil). The method performance was thoroughly investigated, including the analyte stability in wastewater and matrix effect. All target compounds presented linear fits between their LOD and 500ng/L. The quantification limits ranged from 1.6 to 30ng/L for all compounds except for n-octylnortadalafil (LOQ: 100ng/L); precision calculated as intraday repeatability was lower than 30%; accuracy calculated as procedural recovery ranged successfully between 85 and 105% in all cases. The method was applied to samples collected during three week-long monitoring campaigns performed in 2013, 2014 and 2015 in three Dutch cities. Only sildenafil and its two metabolites, desmethyl- and desethylsildenafil, were present with normalized loads ranging from LOQ to 8.3, 11.8 and 21.6mg/day/1000 inh, respectively. Two additional week-long sets of samples were collected in Amsterdam at the time that a festival event took place, bringing around 350,000 visitors to the city. The difference in drug usage patterns was statistically studied: "weekday" versus "weekend", "normal" versus "atypical" week; and results discussed. The metabolite to parent drug concentration ratio evolution during consecutive years was discussed, leading to several possible explanations that should be further investigated. Finally, wastewater-based epidemiology approach was applied to back-calculate sildenafil consumption.

Identification of N-octylnortadalafil and its Stereoisomers in Dietary Supplements with Chiral Liquid Chromatography-Circular Dichroism

A direct chiral liquid chromatography-circular dichroism (LC-CD) method was developed for the simple and rapid identification of N-octylnortadalafil [(6R, 12aR)-6-(1,3-benzodioxol-5-yl)-2-octyl-2,3,6,7,12,12a-hexahydropyrazino[1',2':1,6]pyrido[3,4-b]indole-1,4-dione; RR-OTDF] and its stereoisomers in dietary supplements. Samples were extracted with methanol. Compounds were then separated by chiral LC-CD using Chiralcel OD-RH (4.6 × 150 mm, 5 µm) with 5 mM ammonium formate (pH 3)/0.1% formic acid in acetonitrile (95:5, v/v) mixture solution (mobile phase A) and 0.1% formic acid in acetonitrile (mobile phase B). The isocratic elution used was mobile phase A / mobile phase B (3:7, v/v) at a flow rate of 1 ml/min. The column temperature was held at 30°C. RR-OTDF and its stereoisomers were separated within 20 min with the resolution factors being over 2.0. Using this method, RR-OTDF and (6R, 12aS)-6-(1,3-benzodioxol-5-yl)-2-octyl-2,3,6,7,12,12a-hexahydropyrazino[1',2':1,6]pyrido[3,4-b]indole-1,4-dione were detected in a dietary supplement.

Detection of a tadalafil analogue as an adulterant in a dietary supplement for erectile dysfunction

INTRODUCTION

Several cases of adulteration of dietary supplements with tadalafil, sildenafil, and vardenafil, or their unapproved analogues have been reported worldwide. Mainly, the presence of the latter represents a serious health risk to consumers as their efficacy and toxic effects have not been assessed and may result in unpredictable adverse effects.

AIM

To investigate the suspected adulteration with synthetic phosphodiesterase type 5 (PDE-5) inhibitors in a dietary supplement marketed in Argentina for the treatment of erectile dysfunction (ED).

METHODS

The content of the capsules of the dietary supplement (sample A) was analyzed by thin layer chromatography (TLC) and high-performance liquid chromatography (HPLC) diode-array detection. From the organic extract of sample A, a major compound was purified by column chromatography (CC). The isolated compound was identified by proton nuclear magnetic resonance (1H NMR) and carbon NMR (13C NMR), heteronuclear single quantum coherence, distortionless enhancement by polarization transfer (DEPT 135), electrospray ionization mass spectrometry, and ultraviolet, and infrared (Fourier transform infrared spectroscopy) spectroscopy.

MAIN OUTCOME MEASURE

Proof of adulteration of herbal products with synthetic PDE-5 inhibitors.

RESULTS

By TLC and HPLC analysis, a major compound was detected in sample A organic extract. The purification of this extract by CC led to the isolation of a pure compound which was identified according to its spectral data as (6R,12aR)-2-amino-6-(1,3-benzodioxol-5-yl)-2,3,6,7,12,12a-hexahydropyrazino [1',2':1,6] pyrido [3,4-b] indole-1,4-dione or aminotadalafil.

CONCLUSIONS

An unapproved PDE-5 inhibitor analogue, which was identified as aminotadalafil, has been detected in a dietary supplement. This study represents the first report in Latin America and one of the few independent studies of an adulteration with an unapproved PDE-5 inhibitor of an herbal product for ED treatment.