A polyphenolic-free extract from American cranberry (Vaccinium macrocarpon) was found to inhibit the formation of biofilm by uropathogenic Escherichia coli by over 50%, according to results published in the Journal of Functional Foods.
The new study, led by Professor David Rowley from the University of Rhode Island, concluded that certain carbohydrates in cranberry may also contribute to the fruit’s overall anti-infective properties, in addition to the specific proanthocyanidin content of cranberry.
The potential urinary tract benefits of cranberries have long been linked to its PACs content (specifically the A-type PACs), with a 2004 French health claim stating that North American cranberry with at least 36mg of PAC may “help reduce the adhesion of certain E. coli bacteria to the urinary tract walls”.
“We are looking at a completely different subset of the molecules that you would find in cranberries [beyond the polyphenolics],” said Prof Rowley. “Our results show that they have been overlooked and deserve some attention.”
The research was sponsored by Ocean Spray.
The researchers extracted a phenolic-free carbohydrate fraction from cranberry and identified the constituents as predominantly oligosaccharides possessing various degrees of polymerization. Additional structural analysis revealed that they were mainly xyloglucan and arabinan residues.
Data from antimicrobial assays indicated that the phenolic-free carbohydrate fraction could reduce E.coli CFT073 biofilm production by over 50%, while the same fraction could reduce E. coli MG1655 biofilm production by up to 60%.
“[I]t is possible that the multiple constituents, including polyphenols and oligosaccharides, present in the cranberry whole fruit act additively, complementarily, and/or synergistically in its overall biological effects,” wrote the researchers. “Interestingly, in the current study, we did not observe any growth inhibitory and anti-biofilm effects of the [a] fraction [which was enriched in polyphenol constituents] on both of the E. coli strains […] Therefore, while it appears that the phenolic constituents did not contribute to the inhibition of biofilm formation by the uropathogenic E. coli CFT073 strain (based on our bioassays), their overall contribution to the prevention of urinary tract infections by the whole cranberry fruit should not be discounted.
“Further investigation to clarify the structure–activity relationships of these oligosaccharides is currently being pursued by our group.”
Among Rowley’s team were URI Associate Professor of Biomedical Science Navindra Seeram, who has been cited internationally for his research on blueberries, pomegranate and pure maple syrup and Pharmacy Professor Kerry LaPlante, nationally recognized for her work in the treatment, virulence inhibition, control and prevention of methicillin-resistant Staphylococcus aureus (MRSA) and device-related infections.
Source: Journal of Functional Foods
Volume 17, Pages 235-242, doi: 10.1016/j.jff.2015.05.016
“Cranberry (Vaccinium macrocarpon) oligosaccharides decrease biofilm formation by uropathogenic Escherichia coli”
Authors: J. Sun, et al.