SIMULATED IN VITRO GASTROINTESTINAL DIGESTION AND ITS INFLUENCE ON THE ANTIOXIDANT POTENTIAL OF RAMBUTAN (Nephelium lappaceum) PULP, PEELS, AND SEEDS

The Brazilian Amazon region is home to plant species of great functional and nutritional interest, among which rambutan stands out, a fruit characteristic of the eastern Amazon that draws attention for its high content of vitamin C, organic acids, and bioactive compounds associated with antioxidant properties. The present study aimed to evaluate the effects of simulated in vitro gastrointestinal digestion (oral, gastric, and intestinal phases) on the antioxidant potential of rambutan peel, pulp, and seed fractions using the ABTS, FRAP, DPPH, CUPRAC, and CTR methods, based on the FA1005 INFOGEST protocol. The results showed that the peel fraction initially presented high values, especially for DPPH (95.16%) and FRAP (454.51 mgFe²⁺/g). However, after digestion, particularly in the intestinal phase, there was a significant decrease in these parameters, reaching 65.34% for DPPH and 99.07 mgFe²⁺/g for FRAP, corresponding to losses of more than 75% in reducing activity. This trend was also observed in CTR and CUPRAC, which decreased from 299.85 to 17.46 mgQE/g and from 147.18 to 89.65 mgTE/g, respectively, indicating the high susceptibility of the peel to the degradation of phenolic compounds during the digestive process. In contrast, after digestion, the pulp initially showed lower antioxidant potential, with DPPH at 32.22% and FRAP at only 8.85 mgFe²⁺/g. However, some parameters remained relatively stable after digestion, such as FRAP, which measured 8.66 mgFe²⁺/g in the intestinal phase, suggesting the release of compounds previously bound to the food matrix. However, DPPH activity was higher in the oral phase but decreased in the intestinal phase, while ABTS showed an increasing trend, reaching 64.51% in the intestinal phase, revealing selectivity for compounds with greater affinity for the cationic radical. The seed showed intermediate behavior, with DPPH remaining relatively stable in the oral and gastric phases (approximately 25%), but falling to 13.13% in the intestinal phase. Meanwhile, FRAP and CTR underwent sharp reductions, from 28.91 to 3.02 mgFe²⁺/g and from 69.14 to 9.25 mgQE/g, respectively. On the other hand, CUPRAC and ABTS showed greater resistance, maintaining values of 62.89 mgTE/g and 65.44 mgTE/g at the end of the intestinal phase, suggesting that the seed contains antioxidant compounds that are more stable during digestion. Thus, it was found that the digestive process affects rambutan fractions differently: the peel has greater initial antioxidant potential, while the pulp and seed exhibit greater post-digestion stability, highlighting the consumption of the whole fruit as a strategy against oxidative stress.