Xiaowei Ge

Safety and Quality Assessment of 175 Illegal Sexual Enhancement Products Seized in Red-Light Districts in Singapore

Background: In recent years, there has been increasing interest in the use of herbs and supplements as an alternative to drugs used for the treatment of erectile dysfunction, in order to enhance sexual performance. Over the years, adverse events associated with the consumption of natural health products for sexual enhancement and the treatment of erectile dysfunction have been reported.Objective: The objective of this work was to assess the safety and quality of 175 sexual enhancement health products seized from makeshift stalls in red-light districts of Singapore.Method: Seven raids were conducted by the Health Sciences Authority, Singapore, in two red-light districts in February and March 2008. 175 sexual enhancement health products seized from makeshift stalls were extracted with methanol and screened for Western drug adulterants using high performance liquid chromatography and gas chromatography-mass spectrometry. The labels and claims of the products were also evaluated.Results: Of the 175 products evaluated, 134 (77%) were found to be adulterated with Western drugs or their analogues. Most of these 134 samples (123 [92%]) were found to be adulterated with sildenafil. The extent of adulteration of these illegal health products with Western drugs, including synthetic phosphodiesterase type 5 enzyme (PDE-5) inhibitors, and the risks of consuming such illegal sexual enhancement products are discussed in this study. Because of the scope of the raids, sildenafil was the most common adulterant found. In addition, some products were found to contain high contents of sildenafil (>100 mg) and high contents of the antidiabetic drug, glibenclamide (glyburide). The resultant severe hypoglycaemia has led to ten fatalities.Conclusion: The presence of Western drug adulterants and their analogues in illegal sexual enhancement products seized from red-light districts in Singapore, and their often misleading labels and claims, put the health of consumers at risk. To safeguard public health, greater public awareness of the danger of consuming such illegal products and the lack of quality control of these illegal sexual enhancement health products is important.

Identification of benzamidenafil, a new class of phosphodiesterase-5 inhibitor, as an adulterant in a dietary supplement

A sample labeled to be a natural herbal supplement for the enhancement of sexual function, was sent to Health Sciences Authority (HSA) of Singapore for testing. An unknown compound was detected and isolated from the product. The structure of the unknown compound was identified using LC-UV, high-resolution MS, ESI-MS/MS, IR, and NMR. The compound was characterized as a phosphodiesterase-5 (PDE-5) inhibitor, benzamidenafil. This is the first report of benzamidenafil, representing a new class of PDE-5 inhibitors, as an adulterant of a dietary supplement.

Isolation and structure elucidation of an interaction product of aminotadalafil found in an illegal health food product

An interaction product of aminotadalafil was isolated from an illegal health food product. The structure of the interaction product was elucidated by means of IR, NMR, and mass spectroscopy. The hitherto unknown compound was characterized as condensation product of aminotadalafil and hydroxymethylfuraldehyde and is probably the result of a drug-excipient incompatibility.

Isolation and characterization of propoxyphenyl linked sildenafil and thiosildenafil analogues in health supplements

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.

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

A PDE-5 inhibitor was detected and isolated from a health supplement claimed to be a preparation of fresh oyster extracts and be able to promote and support healthy sexual function and endurance, etc. The structure of this PDE-5 inhibitor was elucidated using LC-UV, LC-TOF-MS, MS-MS, IR spectroscopy, and 2D NMR. It was characterized as 8-(2-(4-(hydroxymethyl)piperidin-1-yl)benzylamino)-3-ethyl-1H-imidazo[4,5-g]quinazoline-2(3H)-thione, a compound reported to be a PDE-5 inhibitor.

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

An unknown compound is detected and isolated from two herbal dietary supplements bought on the internet. The structure of the unknown compound is elucidated using ESI–MS/MS, NMR, UV and IR. The compound, named hydroxythiohomosildenafil, is identified as an analogue of sildenafil in which the oxygen atom is substituted with a sulfur atom in the pyrazolopyrimidine moiety, and a hydroxyethyl group instead of a methyl group is attached to the piperazinyl nitrogen. It is the first report of this compound being detected in herbal dietary supplements. The UV, IR and completely assigned NMR data of hydroxythiohomosildenafil is recorded.

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.

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.

Structural elucidation of propoxyphenyl isobutyl aildenafil, adulterant in a health supplement using high-resolution Orbitrap mass spectrometry

A new sildenafil analogue, propoxyphenyl isobutyl aildenafil has been found in trace quantity from one health supplement. It has been purified by preparative high performance liquid chromatography (HPLC). The structural elucidation of this compound has been carried out using high-resolution Orbitrap mass spectrometry under two fragmentation modes, namely High energy Collision Dissolution (HCD) and Collision Induced Dissolution (CID). Under MS(3) experiments and CID mode, the isobutyl-bonded fragments of propoxyphenyl isobutyl aildenafil at m/z 313 and 297 have been compared with the reference ions derived from isobutyl sildenafil. The accurate mass measurement of each product ions has been carried out with the aid of Mass Frontier software (version 5.0). The mass error of all product ions is not more than 5.0ppm.

Isolation and structural elucidation of a new sildenafil analogue from a functional coffee.

A sildenafil analogue was detected in a functional coffee sample labelled to have male sexual performance enhancement effects. This analogue was isolated and purified by flash chromatography and preparative high-performance liquid chromatography. Its structure was elucidated using high-resolution mass spectrometry; electrospray ionization-tandem mass spectrometry; and nuclear magnetic resonance spectroscopy, ultraviolet spectroscopy, and infrared spectroscopy. Compared with sildenafil, instead of an N-methylpiperazinyl moiety, ring opening of the piperazine ring with the loss of a carbon atom resulted in a substituted benzenesulfonamide. The chemical name of this analogue is N-[2-(dimethylamino)ethyl]-4-ethoxy-3-(1-methyl-7-oxo-3-propyl-6,7-dihydro-1H-pyrazolo[4,3-d]pyrimidin-5-yl)benzenesulfonamide. It is named descarbonsildenafil because it has one less carbon atom when compared with sildenafil.