Adulteration of Cranberry Extracts

Reviewed: Navarro M, Núñez O, Saurina J, Hernández-Cassou S, Puignou L. Characterization of fruit products by capillary zone electrophoresis and liquid chromatography using the compositional profiles of polyphenols: application to authentication of natural extracts. J Agric Food Chem. 2014;62(5):1038-1046.

Cranberry (Vaccinium macrocarpon, Ericaceae) is another botanical where health benefits have been linked to the content of proanthocyanidins (PACs). Unlike grape seed, cranberry extracts contain both A-type and B-type PACs, with A-type making up about 65% of the PACs in the fruit.¹ Cranberries, blueberries, grapes, and raisins and six fruit juices (three made from cranberry and three from grape) were purchased from Barcelona markets. An additional 10 commercial cranberry products were evaluated, i.e., capsules, sachets, natural extracts and a syrup, provided by the dietary supplement and cosmetics manufacturer Deiters, S.L. (Badalona, Spain). The samples were separated by either capillary zone electrophoresis (CZE) or high performance liquid chromatography (HPLC) and detected using UV absorption at 280 nm. The electrophoretic and chromatographic profiles were evaluated statistically by principal component analysis (PCA). For CZE, the results varied, depending on the model selection criteria, but in the optimized model, one commercial extract (extract 1) was located outside the cluster corresponding to cranberry-based products. For the HPLC results, PCA for all data matrices indicated that principal components (PCs) 1, 2, and 3 were indicative of the type of product (i.e., fresh fruit, juice, natural extract, or capsule) regardless of the nature of the fruit. In contrast, a distinction of the type of fruit could only be seen using additional PCs. In this model, cranberry extract 1 clustered with the grape products. This extract was further analyzed by UHPLC-HRMS, but the authors’ conclusions were contradictory with regard to the presence of A-type PACs in the ingredient.

Comment: The A-type PACs, which are rather rare in the plant kingdom, are often regarded as being at least partly responsible for the anti-adherent properties of cranberry products. In addition to cranberry, A-type PACs also occur in cinnamon (Cinnamomum verum, Lauraceae, syn: C. zeylanicum) bark, cacao (Theobroma cacao, Malvaceae), apricot (Prunus armeniaca, Rosaceae) fruit and – as mentioned above – in peanut skins. Since extracts of cranberry or cinnamon are more expensive than grape seed or peanut skin extracts, and a substitution with PAC-containing ingredients is not easily detected, it provides an opportunity for unscrupulous suppliers to adulterate the costly materials for financial gain. The absence of A-type PACs in cranberry products labeled to contain PACs is a clear indication of adulteration; however, it is not clear if a thorough statistical analysis like the one presented by Navarro et al. would be capable of distinguishing between a cranberry extract and a peanut skin extract. Even more challenging is the detection of admixtures of peanut skin extracts to a cranberry product in cases where DNA methods cannot be applied. It would be helpful to make a chemical authentication method specific for cranberry available. The published approaches, in particular the HPLC-UV method, are a first step in the right direction.

Reference

1.     Gu L, Kelm MA, Hammerstone JF, et al. Screening of foods containing proanthocyanidins and their structural characterization using LCMS/MS and thiolytic degradation. J Agric Food Chem. 2003;51:7513-7521.