Metabolite profiling of edible bird's nest using gas chromatography/mass spectrometry and liquid chromatography/mass spectrometry.

RATIONALE: Edible bird's nest (EBN) is a renowned food item in the Chinese community due to the therapeutic effects claimed to be brought about by its consumption. However, very little scientific information has been revealed to support these claims. Thus, metabolite profiling was performed to identify the metabolites and to relate them to the medicinal properties of EBN. The study also aims to further extend the results to determine any possible differences when the EBNs are classified according to their coloration, countries or production sites. METHODS: Extraction of the metabolites was performed via sonication of EBN with methanol and chloroform. Two analytical platforms, namely gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/mass spectrometry (LC/MS), were utilized to detect the metabolites. This multi-analytical platform would provide a comprehensive coverage of the metabolites in EBN. GC/MS analysis was conducted in scan mode from m/z 50-650. On the other hand, LC/MS analysis was operated in both positive and negative ion mode from m/z 150-1000. RESULTS: Metabolites were identified and their relationships with the medicinal properties of EBN were deduced. Classification with chemometrics illustrates that EBNs could be differentiated according to their coloration, countries and production sites. This differentiation was due to the environment where the EBNs are produced. Furthermore, GC/MS was demonstrated to be more suitable for classification as the processing methods of the EBNs did not cause a significant variation in the metabolites detected by GC/MS. CONCLUSIONS: The overall findings suggest that the novel approach of metabolite profiling offers new insights to understanding EBN and provided evidence to support the medicinal properties of EBN. In addition, the success of classification of EBNs with metabolite profiling combining with chemometrics represents a paradigm shift in the quality control of this food item.

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 identification of thiohomosildenafil and thiosildenafil in health supplements.

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.

Determination of isopropyl-9H-thioxanthen-9-one in packaged beverages by solid-phase extraction clean-up and liquid chromatography with tandem mass spectrometry detection.

A simple method was developed and validated for the trace determination of 2-isopropylthioxanthone (ITX) in packaged drinks. Samples were extracted from the food matrix using acetonitrile:water (60:40, v/v), and further subjected to clean-up and preconcentration using solid-phase extraction prior to analysis by liquid chromatography-tandem mass spectrometry using multiple reaction monitoring (MRM) mode. The use of 2-isopropyl-[(2)H7]thioxanthen-9-one was incorporated into the method as an internal standard. Excellent 3-day interday precision data (RSD 0.72%, n=10), and intraday precision data (RSD 0.52%, n=10) were obtained on a 0.10 microg/L standard solution. Spiked samples (n=8) were used to gauge the accuracy of the method at the concentration levels of 2.5, 100, and 500 microg/kg in food; recoveries ranged from 97.0 to 103.0%. These excellent validation data suggest the exciting possibility of using this method for the determination of low levels of ITX migrating from printed food packaging materials into beverages with a method quantitation limit of 0.50 microg/kg. For the first time, analysis on a range of milk, juice, tea and yoghurt drinks, as well as their respective food packaging materials were performed for comparative studies on their ITX content.

Single laboratory validation of a method for the determination of Bisphenol A, Bisphenol A diglycidyl ether and its derivatives in canned foods by reversed-phase liquid chromatography.

A method was developed and validated for the simultaneous determination of Bisphenol A (BPA), Bisphenol A diglycidyl ether (BADGE), BADGE-H2O, BADGE-2H2O, BADGE-H2O-HCl, BADGE-HCl, and BADGE-2HCl in canned food using reversed phase high-performance liquid chromatography (HPLC) with fluorescence detection; chromatographic separation of all seven analytes was achieved (Rs > or = 1.08) using HPLC gradient elution technique. Acetonitrile was used to extract the analytes from the food matrix before subjecting the samples to liquid-liquid extraction, solid-phase extraction for further clean-up and preconcentration prior to HPLC analysis. Excellent inter-day precision data (n = 10) and intra-day precision data (n = 5) were obtained on a 200 microg/kg spiked sample. The RSD ranged from 0.20% to 2.96% for the inter-day precision tests, and 0.04% to 2.82% for the intra-day precision tests. Accuracy was measured at three concentration levels: 200, 1000, and 2000 microg/kg; recoveries ranged from 86.07% to 114.06%. The excellent validation data suggests that this method can be applied on canned foods for the determination of migration of BPA, BADGE and its derivatives from can coatings into food.

Identification of edible Bird's nest with amino acid and monosaccharide analysis.

This study describes the approach of amino acid and monosaccharide combined with Hotelling T2 range plot to identify edible bird nests (EBN) and non-EBN. Prior to the approach, an analytical method was developed and validated to quantify monosaccharides in EBN. Hotelling T2 range plots of both compounds were successful in predicting the different types of EBN and differentiating EBN and non-EBN. This outcome suggests EBN contains a group of glycoproteins which is not affected by the EBN's coloration, country of origin, and/or the processing method of the food item. In addition, the glycoproteins were shown to be unique to EBN. EBN were revealed to be rich in protein and essential amino acids as well as contain a wider variety of monosaccharides than most food items. The overall findings suggest that amino acid and monosaccharide provide information not only on the detected compounds and also insights into the glycoproteins of EBN.

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.

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.