Chemometric Analysis of Low-field 1H NMR Spectra for Unveiling Adulteration of Slimming Dietary Supplements by Pharmaceutical Compounds.

Nao Wu,Véronique Gilard,Saïda Danoun,Myriam Malet-Martino,Stéphane Balayssac

doi:10.3390/molecules25051193

Abstract

The recent introduction of compact or low-field (LF) NMR spectrometers that use permanent magnets, giving rise to proton (1H) NMR frequencies between 40 and 80 MHz, have opened up new areas of application. The two main limitations of the technique are its insensitivity and poor spectral resolution. However, this study demonstrates that the chemometric treatment of LF 1H NMR spectral data is suitable for unveiling medicines as adulterants of slimming dietary supplements (DS). To this aim, 66 DS were analyzed with LF 1H NMR after quick and easy sample preparation. A first PLS-DA model built with the LF 1H NMR spectra from forty DS belonging to two classes of weight-loss DS (non-adulterated, and sibutramine or phenolphthalein-adulterated) led to the classification of 13 newly purchased test samples as natural, adulterated or borderline. This classification was further refined when the model was made from the same 40 DS now considered as representing three classes of DS (non-adulterated, sibutramine-adulterated, and phenolphthalein-adulterated). The adulterant (sibutramine or phenolphthalein) was correctly predicted as confirmed by the examination of the 1H NMR spectra. A limitation of the chemometric approach is discussed with the example of two atypical weight-loss DS containing fluoxetine or raspberry ketone.

Highlights

The adulteration of dietary supplements (DS) with approved or non-approved medicines poses a threat to the health of consumers [1]
Phenolphthalein is used for its laxative properties even though it has been removed from over-the-counter products in the late 1990s due to a carcinogenic risk [6]
The aim of the present study is to deepen the evaluation of LF NMR to detect adulteration of slimming DS by coupling LF 1 H NMR data with a chemometric analysis, allowing classification of samples without expert interpretation of NMR spectra recorded on a low-cost benchtop spectrometer

Summary

Introduction

The adulteration of dietary supplements (DS) with approved or non-approved medicines poses a threat to the health of consumers [1]. The adulteration of slimming preparations with active pharmaceutical ingredients to increase their effects is a widely reported issue [2]. The two most common adulterants detected in weight-loss preparations are sibutramine and phenolphthalein, alone or in combination [3,4,5]. Sibutramine is an anorectic drug that was withdrawn from the market of many countries Various analytical methods have been proposed for the detection and/or quantification of undeclared drugs in slimming DS. Other methods including vibrational spectroscopy [10], gas chromatography [4] or ion exchange chromatography with conductivity detection have been proposed [11]. High-Field (HF) 1 H NMR spectroscopy has been successfully applied for detecting and quantifying adulterants in slimming DS [5]

Objectives

Methods

Results