Analysis of adulterated herbal medicines and dietary supplements marketed for weight loss by DOSY ¹H-NMR

Abstract

Twenty herbal medicines or dietary supplements marketed as natural slimming products were analysed by diffusion ordered spectroscopy (DOSY) ¹H-nuclear magnetic resonance (NMR) and DOSY-COSY ¹H-NMR. The method allows analysis of the whole sample with the detection of both active and inactive ingredients in these complex matrices. Among the 20 formulations analysed, two were strictly herbal and four had a composition corresponding to declared ingredients on the packaging or the leaflet. The others were all adulterated. Eight formulations contain sibutramine alone at doses ranging from 4.4 to 30.5 mg/capsule. Five formulations contain sibutramine (from 5.0 to 19.6 mg/capsule or tablet) in combination with phenolphthalein (from 4.4 to 66.1 mg/capsule), and the last formulation was adulterated with synephrine (19.5 mg/capsule). Quantification of the actives was carried out with ¹H-NMR. Several other compounds were also characterized including methylsynephrine, vitaberin, sugars, vitamins, etc. DOSY NMR is thus proposed as a useful tool for detection of unexpected adulteration.

Keywords:

• Analysis–nuclear magnetic resonance (NMR)
• additives general
• nutritional supplements
• DOSY

Acknowledgements

The authors wish to thank Marie-José Parent and Dr Saleh Trefi for helpful discussion on herbal drug adulteration; and Catherine Claparols for mass spectrometry experiments.