Analytical Chemistry

The Untargeted Capability of NMR Recognizes Adulterated Natural Products


Curcuma longa (turmeric) has a long ethnomedical background for common ailments, and Dietary Supplements (DS) labelled as “Curcumin” (CDS) are a highly visible portion of today’s selfmedication market. Due to cost pressure, these CDS products are affected by economically motivated adulteration with synthetic curcumin and are associated with unexpected toxicological issues due to “residual” impurities. Using a combination of targeted and untargeted (phyto)chemical analysis, this study investigated the botanical integrity of two commercial “turmeric” CDS with vitamin and other additives that were associated with reported clinical cases of hepatotoxicity. Analyzing multi-solvent extracts of the CDS by 100% quantitative 1H NMR (qHNMR), alone and in combination with countercurrent separation (CCS), provided chemical fingerprints that allowed both the targeted identification and quantification of declared components and the untargeted recognition of adulteration. While confirming the presence of curcumin as a major constituent, the universal detection capability of NMR identified significant residual impurities. While the loss free nature of CCS captured a wide polarity range of declared and unwanted chemical components and increased dynamic range, (q)HNMR determined their mass proportions and chemical constitutions. The results demonstrate that NMR can recognize undeclared constituents even if they represent a relatively minor gap in the mass balance of a DS product. The chemical information associated with the missing 4.8% and 7.4% (m/m) in the two commercial samples, exhibiting an otherwise adequate curcumin content of 95.2% and 92.6%, pointed to a product integrity issue and adulteration with undeclared synthetic curcumin. Impurities from synthesis are most plausibly the cause of the observed adverse clinical effects. The study exemplifies how the simultaneously targeted and untargeted analytical principle of 100% qHNMR method, performed with entry-level instrumentation (400 MHz), can enhance the safety of DS by identifying adulterated, non-natural “natural” products

Version notes



Thumbnail image of Kim_McAlpine_AdulteratedNaturalProducts_chemRxiv_20201031.pdf