Simulated Gastrointestinal Digestion of Euterpe precatoria and Euterpe oleracea Açaí Extracts: Phenolic Bioaccessibility and Antioxidant Capacity

Açaí (Euterpe precatoria and Euterpe oleracea) is an Amazonian fruit rich in anthocyanins and antioxidant compounds. However, its functional potential depends on the release and stability of these compounds during gastrointestinal digestion. This study aimed to evaluate the bioaccessibility of total phenolic compounds and antioxidant capacity of aqueous açaí extracts after simulated gastrointestinal digestion.

Aqueous extracts were prepared from commercial açaí powder through exhaustive extraction using an Ultra-Turrax, followed by filtration. Samples underwent oral, gastric, and intestinal phases of the INFOGEST in vitro digestion protocol, in triplicate. Total phenolic content was determined using the Folin–Ciocalteu method, while antioxidant capacity was assessed by ORAC, FRAP, and ABTS assays before and after digestion. Statistical comparisons employed Welch’s t-test (α = 0.05).

Total phenolic content increased from 3.86 to 8.22 mg GAE/g after digestion (+112.7%; apparent bioaccessibility index: 212.7%; p < 0.001), suggesting enhanced release or extractability of phenolic compounds. Antioxidant capacity varied according to the analytical method. FRAP decreased significantly by 83.8% (p < 0.001), whereas ORAC decreased by 72.4%, without statistical significance (p = 0.586). Conversely, ABTS activity increased in both species, showing a progressive increase in E. oleracea (EAOL; +194%, from 152 to 448 µmol TE/L) and a less pronounced, non-monotonic response in E. precatoria (EAP; +39%, from 315 to 440 µmol TE/L). These findings demonstrate species- and assay-dependent responses to gastrointestinal conditions.

The increase in measurable phenolic content may result from enzymatic hydrolysis, structural transformations, and the release of matrix-bound compounds. However, Folin–Ciocalteu measurements may also reflect non-phenolic reducing substances. Differences among antioxidant assays can be attributed to their reaction mechanisms and experimental conditions. ORAC primarily measures hydrogen atom transfer, whereas FRAP and ABTS predominantly involve electron transfer, although their reaction environments and sensitivities differ. Accordingly, the reduction in FRAP alongside increased ABTS activity suggests that digestion modifies antioxidant responses rather than uniformly reducing antioxidant potential. Additionally, gastrointestinal pH changes, anthocyanin transformations, and interactions with digestive components may influence antioxidant activity, particularly during the intestinal phase.

In conclusion, simulated gastrointestinal digestion increased measurable phenolic content while differentially affecting antioxidant capacity in aqueous açaí extracts. Increased ABTS activity in both species contrasted with reductions observed using FRAP and ORAC, emphasizing the importance of complementary analytical approaches. These results support further investigation of species-specific bioaccessibility and functional properties following digestion, including the identification of compounds responsible for the observed antioxidant responses. 

This study was supported by FAPESP (2025/05763-0), CNPq (Universal Project 400122/2025-1 and Research Productivity Fellowship 302264/2026-4).