1H-NMR Study of Cinnamon Spice and Food Supplements from French Markets

Reviewed: Wu N. Low-field NMR for quality control and fraud detection: application to the analysis of dietary supplements and e-liquids. PhD Thesis. Université Paul Sabatier – Toulouse III, 2020. NNT : 2020TOU30044.

Keywords: Adulteration, cinnamon, Cinnamomum verum, Cinnamomum cassia, coumarin, ¹H-NMR

Fourteen samples of cinnamon (Cinnamomum spp., Lauraceae) sold as spice bought in French groceries or shopping malls, and 14 dietary supplements purchased online or in French organic groceries or health food stores, were analyzed by ¹H NMR and further evaluated using multivariate statistics. Spice products indicated an origin from Ceylon (n = 3), Vietnam (n = 2), Madagascar (n = 1), Southeast Asia (n = 1), or Thailand (n = 1), while others did not specify the provenance. Only two food samples included species information on the label, i.e., C. verum (syn. C. zeylanicum) and C. burmanni. Dietary supplements were labeled to contain Ceylon cinnamon (presumably C. verum, n = 4), C. verum (n = 3), C. cassia (n = 5), C. burmanni (n = 1), and one to consist of a mixture of Cinnamomum species.

As part of the method development, a comparison of high-field ¹H NMR (400 MHz) and low-field NMR (60 MHz) was performed. Low-field NMR represents a lower-cost option while still providing useful information for a quality control laboratory. For quantitative analysis using high-field NMR, 15 mg of cinnamon were sufficient to accurately quantify (E)-cinnamaldehyde and coumarin in an hour with limits of quantification (LOQs) of 0.09 mg/g and 0.15 mg/g, respectively. Using the same parameters and recording time on the low-field spectrometer, the LOQs were estimated at 6 mg/g and 10 mg/g for (E)-cinnamaldehyde and coumarin, respectively, due to the approximately 60-fold decrease of the signal-to-noise ratio (SNR). In order to obtain an acceptable SNR ratio for coumarin quantification, the experimental time on the low-field NMR instrument was calculated to be above 100 hours for each sample. Therefore, it was concluded that the low-field NMR approach was not suitable to obtain robust data in a reasonable time frame.

In addition to (E)-cinnamaldehyde and coumarin, high-field NMR allowed quantification of cinnamic acid, cinnamyl alcohol, o-methoxycinnamaldehyde, and eugenol. Species allocation was based on coumarin contents, with two samples having coumarin concentrations of 5.4 mg/g and 6.1 mg/g, respectively, being classified as Saigon cinnamon (C. loureirii), those with concentrations between 1.2–3.6 mg/g as “cassia” (C. cassia or C. burmanni according to the authors), and those with coumarin below the LOQ as C. verum. Eugenol was used as an additional marker to confirm the presence of C. verum.

Two spice products labeled to contain Ceylon cinnamon, or C. verum, were found to contain cassia. Of the 14 dietary supplements, six were made with cassia, two with cinnamon, and two contained cinnamic acid as the main aromatic compound, with small amounts of cinnamaldehyde, and thus could not be classified. The remaining four dietary supplement showed only signals for fatty acids and sugars, and, therefore, were considered to be adulterated.

Comment: The results of this investigation agree with previous investigations showing that most of the food and dietary supplement products labeled to contain cinnamon are made with C. cassia or C. burmanni, both of which are accepted as ‘cinnamon’ by some regulators. It is important to understand that labeling requirements for the various Cinnamomum species on the market vary substantially depending on the country and intended use (i.e., food versus medicine).² However, conclusions in this paper are hampered by the lack of authentic materials representing the different cinnamon species in trade. The classification of species is based on previous results on cinnamaldehyde and coumarin concentrations published by Wang et al.,¹ who also used a limited number of authenticated materials for their investigation, although commercial bulk samples were used as confirmatory ingredients.

The benefits of cinnamon dietary supplements for metabolic disorders has been ascribed mainly to the content of water-soluble proanthocyanidins (PACs), but not necessarily to the contents in cinnamaldehyde and related aromatic compounds of the oil. Nevertheless, the absence of any aromatic compounds in a cinnamon supplement is a clear indication of adulteration.  

References

1. Wang Y-H, Avula B, Nanayakkara NPD, Zhao J, Khan IA. Cassia cinnamon as a source of coumarin in cinnamon-flavored food and food supplements in the United States. J Agric Food Chem. 2013;61(18):4470-4476.
2. Oketch-Rabah HA, Marles RJ, Brinckmann JA. Cinnamon and cassia nomenclature confusion: A challenge to the applicability of clinical data. Clin Pharmacol Ther. 2018;104(33):435-445.