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Jennifer Grebow is editor-in-chief of Nutritional Outlook.
In a new study published in Food Control, researchers tried to analyze and compare the PAC content of 10 different commercially sold cranberry products, including sticks, caplets, tablets, and syrups.
Cranberry supplements are among the most popular herbal supplements on the market. There are many brands of cranberry supplements, but it’s often difficult to tell which products are most effective, primarily because many companies don’t standardize or disclose the level of proanthocyanidins (PACs) in their cranberry products. In a new study published in Food Control1, researchers tried to analyze and compare the PAC content of 10 different commercially sold cranberry products, including sticks, caplets, tablets, and syrups. (The supplements were purchased from pharmacies in France.) Researchers found that the products’ PAC contents varied widely, and they are calling for better standardization of PAC content as well as the need to use the right test methods in order to accurately evaluate PAC levels.
Cranberries are rich in A-type PACs, which studies have linked to bacterial anti-adhesion benefits that help prevent urinary tract infections (UTIs). Due to ranging PAC content across the market, only some cranberry products may contain the recommended daily dosage of PACs (36 mg/day) and thus some cranberry products will be more effective than others at helping to prevent UTIs.
The Food Control study researchers found that 7 of 10 products tested “were found to contain poor-quality PACs ingredient.” As a reference standard, the researchers used a highly standardized, high-PAC-containing cranberry juice from supplier Fruit d’Or Nutraceuticals (Villeroy, QC, Canada). Fruit d’Or was not involved in funding or conducting the study.
The researchers used high-performance thin-layer chromatography (HPLC) to analyze the PAC content in the products, as well as the BL-DMAC reference method to measure PAC content. Because measuring the cranberry PACs using chromatographic techniques alone proved challenging, the researchers combined HPTLC and BL-DMAC to analyze PAC content and also used ultra-high-performance liquid chromatography combined with mass spectrometry (UHPLC-MS) to further confirm the HPTLC results.
The researchers also pointed out that another factor that makes comparing cranberry products difficult and analyzing PAC content difficult is that while some cranberry products contain only cranberry, others may be blended with other ingredients like blueberry, grape seed, and hibiscus. When cranberry is blended with other ingredients, it can be difficult to differentiate between cranberry’s A-type PACs and the B-type PACs more common to other botanicals like grape, cocoa, etc.
Stefan Gafner, PhD, chief science officer of the American Botanical Council (ABC; Austin, TX), commented in a press release on the study results and mentioned problems with analyzing and comparing products in the cranberry market. “My concern is that using HPTLC, or other liquid chromatography-based approaches to determine the authenticity of cranberry supplements, becomes very challenging if these supplements also contain PACs from other sources such as heather or hibiscus,” he said.
Christian Krueger, CEO of testing laboratory Complete Phytochemical Solutions (Cambridge, WI), who has worked with Fruit d’Or to develop improved analytical methods for cranberry, added in the press release: “The authors did a good job at addressing an issue that’s important for the industry: applying analytic tools to asses authenticity and quality of products in the marketplace. One of the challenges of using the UHPLC-MS and HPTLC is that neither of these tools are well-suited for analyzing complex polymeric molecules such as PACs.” For instance, he said, HPTLC will not be able to quantify the ratio of A-type and B-type PACs in a product. Krueger recommends the Matrix Assisted Laser Desorption Ionization Time-of-Flight mass spectrometry (MALDI-TOF) method for analyzing cranberry PACs, which he says may outperform other analytical methods.
“The MALDI-TOF fingerprint is based on PAC structures that are unique to each ingredient,” he said. “MALDI-TOF has demonstrated ability to quantify the relative proportion of blended PAC-enriched ingredients (e.g., cranberry PAC versus apple PAC) within 3% accuracy.”