HPTLC and UHPLC-MS Analysis of Commercial Cranberry Products

Reviewed: Boudesocque-Delaye L, Arnaud Lanoue A, Dorat J, Bruyère F, Gueiffier A, Enguehard-Gueiffier C. Quality control of commercial cranberry products: HPTLC-densitometry a new deal. Food Control. 2018;86:214-223.

Keywords: cranberry, HPTLC, UHPLC-MS, Vaccinium macrocarpon

The quality of dietary supplement products labeled to contain cranberry is known to be variable. Adulteration, in particular with proanthocyanidin (PAC)-rich materials from other low-cost plant sources has been reported on a number of occasions.¹ This study from France investigated the quality of 10 cranberry products sold as sticks, capsules, tablets, and a syrup purchased in French pharmacy stores. The products were evaluated using high-performance thin-layer chromatography (HPTLC) and ultra high-performance liquid chromatography combined with mass spectrometry (UHPLC-MS); in addition, the total PAC content was determined by UV/Vis spectrophotometry after reacting the products with dimethylamino cinnamaldehyde (DMAC).

Only half of the products were labeled to contain cranberry as a single ingredient, while the other five products were combinations including a variety of extracts, i.e., blueberry (Vaccinium angustifolium, V. corymbosum, Ericaceae) fruit, grape (Vitis vinifera, Vitaceae) seed, green tea (Camellia sinensis, Theaceae) leaf, bell heather (Erica cinerea, Ericaceae) flower, or hibiscus (Hibiscus sabdariffa, Malvaceae) calyx extracts. Cranberry juice from Fruit d’Or (Notre-Dame-de-Lourdes, QC, Canada) was used as a reference material.

Unsurprisingly, the HPTLC fingerprints were highly variable. Contents in procyanidin A2, a marker compound found in cranberry, were quantified using HPTLC-densitometry with values between 0-8.73 mg per daily dose. Only one product, a mixture of cranberry and grape seed extract, contained quantifiable amounts (8.40 mg/daily dose) of procyanidin B2. The data from the UHPLC-MS analysis was used for statistical evaluation by principal component analysis. Two products clustered close to the reference product. Other clusters different from the reference included two products containing either grape seed or blueberry extracts in addition to cranberry, and four products, including the cranberry sticks devoid of procyanidin A2, that generally seemed to contain only small amounts of PACs.

Comment: The analysis of cranberry PACs using chromatographic techniques is challenging. PAC polymers containing four or more units are notoriously difficult to separate, so the information obtained is often limited to the determination of monomers, dimers, and trimers. Establishing product quality, and ingredient identity is even more complicated when several PAC-rich plant extracts are combined in a single product. In several of the products analyzed, the presence of cranberry could not be clearly established using HPTLC. Similarly, due to the heterogeneity of the products analyzed, the results of the chemometric analysis remain difficult to interpret: while it allowed for a separation of a number of products into clusters based on A type PAC dimers and trimers (principal component 1), and — to a lesser degree — flavan-3-ol monomers and B type PAC dimers (principal component 2), it is puzzling that four products of a highly different composition according to the labels (including cranberry sticks, a mixture of cranberry with heather and hibiscus sold as syrup, a cranberry extract capsule, and a cranberry hibiscus extract combination capsule) clustered closely together, underscoring the difficulty in interpreting the findings.

Nevertheless, the authors can be commended for their initiative to evaluate the quality of these cranberry products. The comparison of chemical fingerprints is one of the best ways to perform cranberry authentication. On a side note, the common names proanthocyanidin A2 and procyanidin A2 are synonymous, but based on nomenclature guidelines outlined by Ferreira and Slade,² the use of procyanidin A2 is preferred and should be encouraged.

References

1. Cardellina II JH. Adulteration of Cranberry – Botanical Adulterants Bulletin. Austin, TX: ABC-AHP-NCNPR Botanical Adulterants Prevention Program. 2017;1-8.
2. Ferreira D, Slade D. Oligomeric proanthocyanidins: naturally occurring O-heterocycles. Nat Prod Rep. 2002;19:517-541.