1H NMR screening of pharmacologically active substances in weight‐loss supplements being sold online

Abstract

AbstractWeight‐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.