Dietary supplements and medicines are widely marketed over the Internet. Such products may be counterfeited and lack some or all of the labelled ingredients, or, in the case of lifestyle supplements, illegally contain pharmacologically active substances, such as anorectic or androgenic compounds. The market control - especially in the case of customs seizures - is complex, as reference substances necessary for identification and calibration in traditional high performance liquid chromatography (HPLC) or gas chromatography-mass spectrometry (GC-MS) analysis are often unavailable, or extremely expensive. In this study, we introduce a 400 MHz (1) H NMR methodology, which allows identification and quantitative estimation even without such pure compound standards. The identification can be based on literature spectra, or if these data are unavailable, by applying computational NMR spectra prediction. For standardless NMR determination, simple peak-area comparison of the target compound with the TSP reference was used. The applicability was demonstrated for a wide range of compounds, such as mesterolone, oxymetholone, sibutramine, monacolin K, vinpocetine, evodiamine, caffeine, kavain, and dehydroepiandrosterone. The average relative standard deviations were 5.0% for peak area comparison, and 3.3% for external calibration with standard substance. The method uncertainty is therefore higher in standardless determination, but acceptable for the purpose of proving the presence or absence of pharmacologically active substances. The limit of detection of 0.5-2 mg/kg is sufficient for the purpose. NMR is ideally suited to controlling dietary supplements or illegal medicines as it provides qualitative and at least semi-quantitative information more rapidly (measurement time 20 min) than with any other currently available spectroscopic or chromatographic method.

BackgroundRed yeast rice (i.e., rice fermented with Monascus spp.), as a food supplement, is claimed to be blood cholesterol-lowering. The red yeast rice constituent monacolin K, also known as lovastatin, is an inhibitor of the hydroxymethylglutaryl-CoA (HMG-CoA) reductase. This article aims to develop a sensitive nuclear magnetic resonance (NMR) method to determine the total statin content of red yeast rice products.MethodsThe total statin content was determined by a 400 MHz 1H NMR spectroscopic method, based on the integration of the multiplet at δ 5.37-5.32 ppm of a hydrogen at the hexahydronaphthalene moiety in comparison to an external calibration with lovastatin. The activity of HMG-CoA reductase was measured by a commercial spectrophotometric assay kit.ResultsThe NMR detection limit for total statins was 6 mg/L (equivalent to 0.3 mg/capsule, if two capsules are dissolved in 50 mL ethanol). The relative standard deviations were consistently lower than 11%. The total statin concentrations of five red yeast rice supplements were between 1.5 and 25.2 mg per specified daily dose. A dose-dependent inhibition of the HMG-CoA reductase enzyme activity by the red yeast rice products was demonstrated.ConclusionA simple and direct NMR assay was developed to determine the total statin content in red yeast rice. The assay can be applied for the determination of statin content for the regulatory control of red yeast rice products.

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Weight-loss or slimming food supplements may be adulterated with synthetic pharmaceuticals, such as anorectic, anxiolytic and antidepressant compounds, especially when sold over the internet. An NMR screening method to detect these pharmacologically active compounds in slimming products is introduced in this study. As a first step, we gathered NMR-related information ( chemical shifts, multiplicity ) both from the scientific literature and own theoretical spectra prediction for 53 substances, which are likely to be illegally present in weight-loss products. The experimental strategy consists of dissolving the samples in a proper solvent ( most commonly ethanol ) and manually comparing each observed chemical shift with table values and thus identifying possible adulteration. A compound is considered to be identified if all the compound's resonances were present with correct multiplicity ( finally confirmed by J-resolved 2D spectra ). The method has been introduced in routine practise in our institute and we have already detected sibutramine, caffeine and L-carnitine in slimming products. Furthermore, quantification can be conducted by simple integration of a target resonance in comparison with the internal reference standard ( e. g., TSP ), or by using standard solutions ( when available ). We believe that NMR is ideally suited to controlling dietary supplements as it provides qualitative and at least semi-quantitative information more rapidly ( measurement time of about 20 min ) than with any other currently available spectroscopic or chromatographic method. Future research regarding the automation of spectral processing and inclusion of non-targeted analysis is necessary.