An exploratory study published in Food & Function identified and quantified red raspberry polyphenols and their metabolites after human consumption. It characterized an array of polyphenols in different forms of red raspberries and a greater number of phenolic compounds in human biological samples than previous studies. Understanding the metabolic fate of polyphenol compounds in human biological specimens may aid in designing future studies, including mechanism of action studies.

In this study, the most abundant polyphenols in red raspberries were anthocyanins and ellagitannins, which have gained some attention as phytochemicals. Anthocyanins may possess anti-inflammatory, anti-oxidative and metabolic stabilizing activity. Some limited animal and in-vitro studies have shown breakdown products of ellagitannins may help reduce oxidative stress and inflammation.

This study identified polyphenols in four different forms of red raspberries (frozen, fresh, freeze-dried, pureed) and found that while the different forms have relatively similar polyphenol profiles, the concentration of anthocyanins was highest in the frozen red raspberry form and the concentration of ellagitannins was highest in the freeze-dried red raspberry powder form.

“To design studies investigating their biological effects, we needed to have a better understanding of the variability in key polyphenols among red raspberry fruit forms and their metabolic fate in humans after acute and chronic intake of red raspberries,” commented Britt M. Burton-Freeman, PhD, MS of the Center for Nutrition Research, Institute for Food Safety and Health, Illinois Institute of Technology, and senior author of the paper.

This study assessed biological samples (urine, plasma) obtained from two human pilot studies after consuming red raspberries for more than one week. The study tentatively identified 62 red raspberry polyphenol metabolites, including some phenolic compounds that were detected for the first time, in plasma and urine.

The results of this study may offer new information for understanding the metabolic fate of red raspberry compounds and their composition in different biological specimens.

“The knowledge of metabolites detected in human biological samples may aid research platforms in determining which metabolites may be most relevant, and possible mechanisms of action,” said Burton-Freeman.

“We are excited about the direction this study provides in establishing methods for future trials,” commented Tom Krugman, Executive Director of the National Processed Raspberry Council (NPRC). “Our Council is committed to delivering the highest quality nutrition and health science that consumers can apply in making healthy food choices.”

For the study abstract, click here.