Botanical Adulterants Monitor: Issue 20, September 2020

Undeclared Hibiscus and Mulberry Detected in Commercial Cranberry Extracts

Reviewed: 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.

Keywords: Adulteration, cranberry, Hibiscus sabdariffa, Morus spp., Vaccinium macrocarpon, UHPLC-UV/Vis, UHPLC-UV/Vis-MS

Dietary supplements made with cranberry (Vaccinium macrocarpon, Ericaceae) are popular for supporting urinary tract health and are used therapeutically for preventing or treating symptoms of lower urinary tract infections. Available products include cranberry extracts, dried juice, powdered cranberry, and powdered cranberry press cake, which is a byproduct of the cranberry juice industry. Gardena et al. compared the anthocyanin, flavan-3-ol monomer, dimer, trimer, and total proanthocyanidin (PAC) composition of 17 bulk cranberry extracts (from US and European suppliers) and 10 food supplements sold in Italy with those of seven samples of ripe cranberries representing different cultivars. Extracts of the following possible adulterants were provided by Specchiasol (Bussolengo, VR, Italy): chokeberry (Aronia melanocarpa, Rosaceae) fruit, European elder (Sambucus nigra, Adoxaceae) fruit, blackberry (Rubus fruticosus, Rosaceae) fruit, blackcurrant (Ribes nigrum, Grossulariaceae) fruit, red raspberry (Rubus idaeus) fruit, cherry (Prunus serotina, Rosaceae) fruit, black bean (Phaseolus vulgaris, Fabaceae) seed, black soybean (Glycine max, Fabaceae) seed, grape (Vitis vinifera, Vitaceae) seed, pine (Pinus spp., Pinaceae) bark, hibiscus (Hibiscus sabdariffa, Malvaceae) flower, and black mulberry (Morus nigra, Moraceae) fruit.

Total anthocyanins and total proanthocyanidins (PACs) were measured by spectrophotometry. Individual anthocyanins and flavan-3-ol monomers, dimers, and trimers were quantified by ultrahigh-performance liquid chromatography with ultraviolet/visible (UV/Vis) and orbitrap mass spectrometric (MS) detection. Four of the bulk extracts and six food supplements had a different anthocyanin fingerprint from that of authentic cranberry. Based on the anthocyanins present, the adulterants were either identified as hibiscus (n = 2) or black mulberry (n = 1) or could not be assigned. Regarding the flavon-3-ol composition, the authors noticed a relatively consistent ratio of epicatechin to catechin in authentic cranberry fruit, which varied between 6:1 and 10:1. Authentic bulk extracts had epicatechin to catechin ratio of 9.7 ± 2.2, while adulterated bulk extracts had an average ratio of 0.4 ± 0.1. This indicates that contrary to authentic cranberry, catechin was the dominant monomer in the adulterated extracts, making up to 80% of all flavan-3-ol monomers. Hibiscus (0.4), pine bark (0.9), black mulberry (1.1), blackcurrant (0.7), elder (1.3), grape seed (1.1), chokeberry (1.9) and black bean (0.3) extract also had low epicatechin to catechin ratios. On the contrary, the ratio for blackberry and cherry was 27.3 and 4.3, respectively. Procyanidin A2 was the predominant (90%) dimer in cranberry fruit and authentic bulk extracts, while adulterated bulk extracts made only 20-30% of all flavon-3-ol dimers. Interestingly, the amounts of total PACs were in agreement with those specified by the vendors, with the exception of one of the authentic bulk materials. Results obtained for the food supplements were similar, although five products contained less than 70% of the total PACs declared on the label.

Overall, 10 of the 27 samples (37%) were adulterated. The anthocyanin fingerprint, and the epicatechin-catechin ratio are considered important for authentication of cranberry products.

Comment: This investigation confirms earlier reports about the widespread incidence of cranberry extract adulteration, as previously documented in the Botanical Adulterants Prevention Bulletin on Cranberry.¹ The results are especially troubling for food supplements, where six out of 10 were found to contain extracts from other plant species. While the authors included several known or suspected cranberry adulterants, they still were not able to assign the source material in a majority of the cases, suggesting that unknown anthocyanin-rich extracts, or extract blends are sold labeled as cranberry.

As reported by Brown et al.,^2,3 the anthocyanin fingerprint of cranberry is relatively consistent, and, therefore, represents an easy measurement for cranberry authenticity (except in liquid formulations, where anthocyanins degrade quickly unless appropriate measures to stabilize these pigments are taken). Of use for the dietary supplement manufacturing industry is the assessment of the epicatechin-to-catechin ratio. This ratio can be easily measured using conventional HPLC-UV methods, and may provide an additional indication for adulteration if it is below 5.

References

1. Brendler T, Gafner S. Adulteration of cranberry (Vaccinium macrocarpon). Botanical Adulterants Prevention Bulletin. Austin, TX: ABC-AHP-NCNPR Botanical Adulterants Prevention Program; 2017:1-8.
2. Brown PN, Turi CE, Shipley PR, Murch SJ. Comparison of large (Vaccinium macrocarpon Ait.) and small (Vaccinium oxycoccus L., Vaccinium vitis-idaea L.) cranberry in British Columbia by phytochemical determination, antioxidant potential, and metabolomic profiling with chemometric analysis. Planta Med. 2012;78(6):630-640.
3. Brown PN, Shipley PR. Determination of anthocyanins in cranberry fruit and cranberry fruit products by high-performance liquid chromatography with ultraviolet detection: single-laboratory validation. J AOAC Int. 2011;94(2):459-466.