Botanical Adulterants Monitor: Issue 20, September 2020

1H-NMR Study of Cranberry Dietary Supplements Shows Substantial Differences in Composition

Reviewed: Turbitt JR, Colson KL, Killday KB, Milstead A, Neto CC. Application of 1H-NMR-based metabolomics to the analysis of cranberry (Vaccinium macrocarpon) supplements. Phytochem Anal. 2020;31(1):68-80.

Keywords: Adulteration, anthocyanins, ascorbic acid, cranberry, ¹H-NMR, HPLC-Vis, Vaccinium macrocarpon

In this study, the chemical composition of nine commercial cranberry (Vaccinium macrocarpon, Ericaceae) dietary supplements purchased from the internet, or from local vendors in the USA, were compared to authentic cranberry freeze-dried powder from the Cranberry Institute (Carver, MA) and from NIST (Gaithersburg, MD). The authors used proton nuclear magnetic resonance (¹H-NMR) fingerprints with subsequent principal component analysis (PCA) to compare the products. Quantitative NMR allowed the authors to measure the concentrations of citric, malic, quinic, oleanolic, and ursolic acids. Anthocyanins were analyzed by high-performance liquid chromatography with visible detection (HPLC-Vis). Total phenolics were measured by the Folin-Ciocalteau method and total proanthocyanidins (PACs) were determined using the DMAC assay.

Based on the ¹H-NMR results, two dietary supplements showed a composition similar to the reference cranberry powders, while others exhibited a markedly different composition. Overall, hyperoside and malic, oleanolic, quinic, and ursolic acids were found to be the main contributors for the differences among products based on the loadings plot. Four supplements contained little to no triterpenes (oleanolic and ursolic acids), while three were devoid of organic acids (citric, malic, and quinic acids). Three products were devoid of PACs, and three others had no anthocyanins. However, those six supplements where anthocyanins were found exhibited the same anthocyanin pattern as the reference samples. Some of the discrepancies can be explained by the difference in the manufacturing process. Two dietary supplements, labeled to contain cranberry concentrates, generally had a very low content in cranberry metabolites. One product, claiming to contain PACs, was devoid of organic acids and triterpenes. One product labeled as cranberry juice concentrate and vitamin C contained only ascorbic acid, but no cranberry metabolites.

Comment: Similar to the publication on commercial cranberry products by Gardena et al.,¹ the authors used a number of orthogonal methods to determine the quality of dietary supplements claiming to contain cranberry. The data provide a good view of the cranberry market, and the large variability in the composition of commercial cranberry dietary supplements. Interestingly, products marketed as cranberry juice concentrate or cranberry concentrate were of the lowest quality, although the small number of test samples does not allow a more general assessment of this.

Of note, while the ¹H-NMR data are very useful for comparing the composition of the products, the content of individual anthocyanins could not reliably be determined using quantitative NMR. According to the authors, this is “likely due to the overlapping of the many signals generated from the structurally similar cyanidin and peonidin glycosides.”

Reference

1. Gardena C, Scialpi A, Fachechi C, Simonetti P. Identification of markers for the authentication of cranberry extract and cranberry-based food supplements. Heliyon. 2020;6:e03863.