Bioaccessibility analysis of anthocyanins and ellagitannins from blackberry at simulated gastrointestinal and colonic levels

Abstract

The total bioaccessibility of the main phenolic compounds from blackberry fruit using an in vitro gastrointestinal model with colonic fermentation was investigated. The incorporation of a dialysis membrane before starting the fermentation phase was included with the aim of providing more correct bioaccessibility estimations at colonic level. Phenolic compounds in the raw material and in digested samples were analyzed by high-performance liquid chromatography. The intestinal bioaccessibility was 1.8% for the principal anthocyanin, cyanidin-3-O-glucoside, and less than 1% for the principal ellagitannins, lambertianin A and C. In contrast, this value was 14.9% for ellagic acid, due to its release from ellagitannin breakdown. The intestinal bioaccessibility of total polyphenols, calculated as the sum of indigenous phenolic compound contents, was 2.2%. After fermentation, only 1% of the indigenous individual polyphenols was potentially bioaccessible at colonic level. However, ellagic acid colonic bioaccessibility was around 10% due to the prevention of its further metabolization by dialysis process. Total bioaccessibility of the main blackberry polyphenols, calculated as the sum of intestinal and colonic bioaccessibility, was around 3.3%, indicating that gastrointestinal and colonic conditions affected the amount of the indigenous polyphenols and, consequently, their bioaccessibility as intact structures.