Stability, bioaccessibility and antioxidant activity of phenolic compounds from juá fruit exposed to gastrointestinal digestion coupled with a simulated intestinal barrier

The juá (Ziziphus joazeiro) is a specie characteristic from Brazilian semiarid. Consumed by the local population, the edible yellow berries of juá fruit are related to health benefits according the traditional medicine. Increased attention has been devoted to juá fruit e due its phenolic compounds with antioxidant potential. However, the beneficial effects of these compounds largely depend of their luminal release and subsequent intestinal absorption during digestion. Thus, the aim of the present study was to determine the effects of in vitro gastrointestinal digestion (GID) on the bioaccessibility index and stability of polyphenolic compounds, and to determine the antioxidant activity of the intestinal fraction of juá fruits collected in four distinct regions of Brazilian semiarid. The GID was performed using a dynamic model simulating physiological gastrointestinal conditions (oral, gastric and intestinal phases) with enzymes and coupled with a simulated intestinal barrier (cellulose dialysis membrane 12,000 Da). The GDI fractions obtained gastric, intestinal, serum (bioacessible fraction) and colon (non bioacessible fraction) phases were used to analyze the stability phenolic compounds determined by HPLC-DAD, while the antioxidant activity was determined using ORAC, DPPH and FRAP assays. The phenolic compounds identified in non-digested fraction were majority flavonols: catechin (0.9-2.78 mg 100 g-1), epicatechin (0.10-0.12 mg 100 g-1), epicatechin gallato (2.26-12.03 mg 100 g-1), procyanidin B1 (0.28-3.28 mg 100 g-1), quercetin 3- glucosídeo ( 0.30-0.60 mg 100 g-1), ruin (0.13-0.3mg 100 g-1), kampferol (0.10-0.33 mg 100 g-1), gallic acid (1.40-2.10 mg 100 g-1), caffeic acid (0.62-1.4 mg 100 g-1), resveratrol (0.35-1.60 mg 100 g-1). The concentration of all detected phenolic compounds decreased trough GID. The bioacessible fraction presented only catechin, epicatechin gallato, procyanidin B1 and kampferol and the scavenging properties of the bioacessible fraction decreased by 95 %, 96%, 96.5% in ORAC, FRAP and DPPH assay, respectively, with reference to non-digested sample. At the end of GID process, the bioaccessibility of phenolic compounds detected were 17-9% for catechin, 26% for epicatechin, 23.88% for epicatechin gallate, 13-22% for epigallocatechin gallate, 10-15% for proyanidin B1. These compounds may be due action of intestinal and digestive enzymes that facilitate the release of phenolic bound to cell wall polysaccharides and proteins. Only juá fruits from Agreste region present procyanidin B2 in the bioacessible fraction with 18.21% of bioacessibility. The bioaccessible fraction present highest antioxidant capacity for scavenging oxygen radical (135.10 - 97 uM 100 g-1) when compared capacity of scavenging DPPH radical (6.00-13.41 uM 100 g-1) or iron chelating activity (33.66-50.95 uM 100 g-1). The non bioacessible fraction (colon) showed the highest antioxidant potential 733.32-1291.12 uM 100 g-1, 268.38-400 uM 100 g-1 and 216.71-400 uM 100 g-1 by ORAC, FRAP and DPPH assays, respectively. These results clearly showed the effects of GDI on phenolic compounds of juá fruit reducing the amounts available for absorption into the intestinal wall and presented a relevant content phenolic compounds present in colon intestinal.