GASTROINTESTINAL DIGESTION AND EX VIVO COLONIC FERMENTATION MODIFY THE PHENOLIC TRANSFORMATIONS OF GRUMIXAMA (Eugenia brasiliensis Lam.) PROCESSING RESIDUE

Fruit-processing residues are an underused source of phenolic compounds and a promising raw material for functional ingredients, in line with circular economy strategies. However, their potential health effects depend on how these compounds change during digestion and during metabolism by the gut microbiota, which remains poorly characterized. This gap is especially relevant for native Brazilian fruits such as grumixama (Eugenia brasiliensis Lam.), whose residue is a potential source of anthocyanins and ellagitannins. This study investigated how the phenolic profile of grumixama residue changes during simulated gastrointestinal digestion and ex vivo colonic fermentation. The residue consisted of peels and seeds obtained after pulp separation in a horizontal pulper. Phenolic compounds were quantified by high-performance liquid chromatography coupled with a diode array detector (HPLC-DAD), and urolithins were evaluated by HPLC-DAD coupled with mass spectrometry (HPLC-DAD-MS). Results were expressed as mg/100 g of residue (dry weight). Cyanidin-3-O-glucoside and cyanidin were identified in the gastric phase but not after intestinal digestion. This is consistent with the pH-dependent instability of anthocyanins. The flavylium cation predominates under acidic conditions but converts into less stable pseudobases and chalcones as pH increases, favoring degradation. In contrast, intestinal digestion increased ellagic acid from 13.6 mg/100 g to 143.7 mg/100 g (about 10-fold) and 3,4-dihydroxybenzoic acid from 6.4 mg/100 g to 132.9 mg/100 g (about 20-fold). The increase in ellagic acid likely reflects the release and/or depolymerization of matrix-bound ellagitannins. 3,4-Dihydroxybenzoic acid may also arise from the degradation of cyanidin, whose B-ring yields this phenolic acid under neutral to alkaline conditions. The intestinal fraction was then fermented for 72 h in a culture medium inoculated with human feces as the source of the gut microbiota. Ellagic acid and 3,4-dihydroxybenzoic acid decreased by 91.4% and 31.1%, respectively, which indicates extensive microbial biotransformation, particularly of ellagic acid. No urolithins were detected. This result is consistent with urolithin metabotype 0, the inter-individual phenotype in which the gut microbiota cannot convert ellagic acid into detectable urolithins. Overall, grumixama residue is a source of ellagitannin-derived phenolics that become markedly more bioaccessible during upper gastrointestinal digestion. However, their colonic fate depends on each individual’s microbiota composition. These findings support valorizing grumixama residue as a functional ingredient. They also show that metabotype stratification of fecal donors should be considered when evaluating the colonic metabolism of ellagitannin-rich foods. 

Acknowledgments: CAPES (Finance Code 001; 88887.116490/2025-00), CNPq (310912/2022-9), and FAPERJ (E-26/211.286/2021; E-26/210.082/2023; E-26/210.136/2023; E-26/200.027/2026; E-26/200/028/2026).