Open AccessThe Untargeted Capability of NMR Helps Recognizing Nefarious Adulteration in Natural Products
Author(s) -
Seon Beom Kim,
Jonathan Bisson,
J. Brent Friesen,
Luca Bucchini,
Stefan Gafner,
David C. Lankin,
Shao-g Chen,
Guido F. Pauli,
James B. McAlpine
Publication year - 2021
Publication title -
journal of natural products
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.976
H-Index - 139
eISSN - 1520-6025
pISSN - 0163-3864
DOI - 10.1021/acs.jnatprod.0c01196
Subject(s) - curcumin , chemistry , natural product , proton nmr , nuclear magnetic resonance spectroscopy , chemical constituents , traditional medicine , chromatography , organic chemistry , medicine , biochemistry
Curcuma longa (turmeric) has an extensive history of ethnomedical use for common ailments, and "curcumin"-containing dietary supplements (CDS) are a highly visible portion of today's self-medication market. Owing to raw material cost pressure, CDS products are affected by economically motivated, nefarious adulteration with synthetic curcumin ("syncumin"), possibly leading to 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 multisolvent extracts of the CDS by 100% quantitative 1 H 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 spectroscopy identification of significant residual impurities, including potentially toxic components. While the loss-free nature of CCS captured a wide polarity range of declared and unwanted chemical components, and also increased the dynamic range of the analysis, (q)HNMR determined their mass proportions and chemical constitutions. The results demonstrate that NMR spectroscopy can recognize undeclared constituents even if they represent only a fraction of the mass balance of a dietary supplement 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%, respectively, 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 the 100% qHNMR method, performed with entry-level high-field instrumentation (400 MHz), can enhance the safety of dietary supplements by identifying adulterated, non-natural "natural" products.