EFFECT OF IN VITRO GASTROINTESTINAL DIGESTION ON PHENOLIC COMPOSITION AND ANTIOXIDANT CAPACITY OF COMMERCIAL PULPS OF PURPLE AND WHITE AÇAÍ (Euterpe oleracea Mart.)

Açaí is a fruit from the açaí tree, commonly known as açaizeiro (Euterpe oleracea Mart.), which is often used to obtain pulps. These are classified as coarse, medium and fine according to the amount of water added during processing. Commercially, pulps of purple and white açaí can be found. The objective of this study was to evaluate and compare the action of in vitro digestion (IVD) upon the total phenolic compounds (TPC) content and antioxidant activity of purple and white açaí pulps. Three purple açaí samples (coarse-AG, medium-AM and fine-AF) and one of white açaí (coarse-AB) were purchased in Belo Horizonte, Minas Gerais, Brazil. The samples were submitted to IVD, covering the gastric and intestinal phases. In order to evaluate the TPC content and the antioxidant activity of the pulps before and after IVD through the capture of free organics radicals DPPH and ABTS•+ and iron reduction (FRAP) by spectrophotometry, the samples were submitted to methanolic and acetone extraction. The results were evaluated through analysis of variance and Tukey’s test, at 5% significance (Sisvar-5.6). Correlations between TPC content and antioxidant activity after IVD were established using Pearson's coefficient (SPSS). Regarding the TPC, all the samples differed from each other, with the AG sample (583.79 mgGAE/100g) having the highest content, followed by AM, AF and AB with 400.33; 312.33; 180.55 (p<0.05) respectively. After digestion, it was verified that AM (32.27%) presented the highest bioaccessible fraction, being statistically different (p<0.05) from AF (27.05%), AB (25.69%) and AG (22.89%). Similarly to TPC, the AG sample (74.34 µM ferrous sulfate/g) showed higher antioxidant activity in the FRAP test, followed by AM (45.80), AF (24.69) and AB (19.74). Likewise, in the ABTS test, the AG sample (55.05 µM of Trolox/g) was higher, followed by AM (48.68); however, the AF (11.49) and AB (13.69) samples didn’t differ from each other, statically. Only in the DPPH, no significant differences were found between AG (1986.66 EC50 expressed g/g of DPPH) e AM (2408.88); however, the AF sample (3167.14) and AB (4673.15) differed from each other. Decreases in the antioxidant activity of the pulps were observed after digestion. Regarding the FRAP, the highest reduction was observed in the AG sample (80.52%), followed by AM (73.79%); AF (69.10%) and AB (68.88%). In ABTS, the highest reduction was in AM (73.79%) followed by AG (78.30%); AF (71.21%) and AB (55.66%). As for DPPH, the AM sample (13711.40 EC50) showed the lowest reduction in antioxidant activity after digestion, followed by AG (13651.87); AF (28060.03) and AB (47369.0). It is emphasized that the lower the EC50, the greater the antioxidant stability. Strong significant correlations were found between the TPC and the antioxidant activity after IVD (FRAP r=0.908, p<0.01/ ABTS r=0.925, p<0.01/ DPPH r=-0.928, p<0.01), as expected. From these data it is concluded that the TPC content and antioxidant activity of the pulps decrease after an IVD, making it clear that future studies, especially by means of clinical trials, are pertinent to evaluate the bioavailability and biologic activity of the phenolic compounds.