Gastrointestinal digestion assays for evaluating the bioaccessibility of phenolic compounds in fruits and their derivates: an overview.

Fruits and their derivatives are sources of phenolic compounds, which contribute to the maintenance of health benefits. In order to exert such properties, these compounds must be exposed to gastrointestinal conditions during digestion. In vitro methods of gastrointestinal digestion have been developed to simulate and evaluate the changes that compounds undergo after being exposed to various conditions. We present, in this review, the major in vitro methods for evaluating the effects of gastrointestinal digestion of phenolic compounds in fruits and their derivatives. We discuss the concept of bioaccessibility, bioactivity, and bioavailability, as well as the conceptual differences and calculations among studies. Finally, the main changes caused by in vitro gastrointestinal digestion in phenolic compounds are also discussed. The significant variation of parameters and concepts observed hinders a better evaluation of the real effects on the antioxidant activity of phenolic compounds, thus, the use of standardized methods in research would contribute for a better understanding of these changes.

Biotransformation of the Brazilian Caatinga fruit-derived phenolics by Lactobacillus acidophilus La-5 and Lacticaseibacillus casei 01 impacts bioaccessibility and antioxidant activity.

This study aims to evaluate the effect of fermentation of fruit purees (seriguela, mangaba, mango, and acerola) with Lacticaseibacillus casei 01 and/or Lactobacillus acidophilus LA-05 on the profile and bioaccessibility of phenolics and antioxidant activity. The physicochemical parameters and sugar and organic acid contents were also measured for evaluating the fermentation system. Fruit purees were adequate substrates for the growth of probiotic cultures, presenting high viability in the product and after simulated gastrointestinal conditions (≥7 log CFU/g). The fermentation with probiotic cultures increased the lactic acid (8.45-15.44 mg/mL), acetic acid (0.05-1.05 mg/mL), and phenolic contents and bioaccessibility, while the pH values and glucose and fructose contents were decreased (p < 0.05). L. acidophilus was found in higher counts in seriguela puree (8.00 ± 0.03), resulting in a higher consumption of maltose, fructose, and glucose, increased phenolic compounds content and bioacessibility and higher antioxidant activity (p < 0.05). The co-cultivation of both probiotic strains showed promising results for mango, mangaba and seriguela purees, resulting in an increased content and bioaccessibility of phenolics and higher antioxidant activity (p < 0.05). Our findings demonstrate for the first time that the Brazilian Caatinga fruit-derived phenolics can be biotransformed by Lactobacillus and amended genera probiotics to bioaccesible phenolics with antioxidant activity. The knowledge obtained from this study will provide fundamental concepts of the use of synergistic probiotics for future fermentation of other fruit purees to increase the bioaccesibility and antioxidant activity of biotransformed phenolic compounds.

Juá fruit (Ziziphus joazeiro) from Caatinga: A source of dietary fiber and bioaccessible flavanols.

Fruits from Ziziphus joazeiro from Mata Paraibana (MP), Borborema (BB), Agreste (AG) and Sertão Paraibano (SP) were assessed to determine their morphological characteristics, nutritional composition, content and bioaccessibility of phenolic compounds and antioxidant activity. In general, juá fruits presented ovoid shape, high moisture (65.33-72.53%), low acidity, with succinic acid being the predominant organic acid, and high dietary fiber content (8.98-10.81%), mostly insoluble fibers (5.72-8.02%). Fruits from MP presented the highest amounts of free phenolic compounds (24.27 mg/100 g) and the highest antioxidant activity in the DPPH, FRAP and ORAC assays. In MP fruits, epigallocatechin gallate (12.04 mg/100 g) was the major compound, while in fruits from other states, phenolic compounds were the major compounds. The bioaccessibility of catechin, epicatechin, epicatechin gallate, epigallocatechin gallate, procyanidin and syringic acid varied among fruits from different regions. Fruits from SP presented the highest phenolic content in the bioaccessible fraction and highest antioxidant activity in all assays. The findings of this study indicate that juá is a non-acidic fruit with highest moisture, source of fiber, majority insoluble fibers and bioaccessible flavanols.

Bioaccessibility of phenolic compounds in native and exotic frozen pulps explored in Brazil using a digestion model coupled with a simulated intestinal barrier.

The bioaccessibility of phenolics and antioxidant activity were determined in açaí, cupuaçu, blackberry, blueberry, jabuticaba, raspberry, cajá and soursop frozen pulps (FPs) using a digestion model coupled with a simulated intestinal barrier. Cyanidin 3-glucoside (6.56%) and pelargonidin 3-glucoside (28.33%) were bioaccessible in blueberry and raspberry. Catechin had the highest bioaccessibility in blueberry (270.71%), blackberry (137.51%), and jabuticaba (99.52%), while the highest bioaccessibility of epicatechin (153.59%) and syringic acid (147.14%) was observed in blueberry. Procyanidin B1 presented the highest bioaccessibility in cajá (102.79%) and blackberry (87.62%) and contributed to the high DPPH▪ scavenging activity observed in these FPs. The bioaccessible fraction in soursop consisted of caffeic (8.18%), p-coumaric (7.36%), caftaric (7.96%) and chlorogenic (11.08%) acids, and these acids were correlated with the iron reduction capacity of this FP. Our study assessed the bioaccessible phenolics in several FPs and showed that those found in cajá and blackberry possesses the highest antioxidant activity.

Bioaccessibility and antioxidant activity of phenolic compounds in frozen pulps of Brazilian exotic fruits exposed to simulated gastrointestinal conditions.

This study characterized the phenolic profile in siriguela, umbu-cajá and mangaba, as well in their frozen pulps (FPs). The bioaccessibility of phenolic compounds and the antioxidant activity of the FP dialysates were determined following exposure to simulated gastrointestinal conditions. The profile of phenolic compounds identified in fruit and FPs were relatively similar. After pulp processing, increases of 33.60% and 68.72% in free phenolics were observed for mangaba and umbu-cajá, respectively, whereas in siriguela, the free phenolic was reduced by 56.55%. Generally, phenolic levels decreased after exposure to simulated gastric conditions in all FPs. The bioaccessibility of phenolics varied among the evaluated FPs. The highest bioaccessibility was observed for gallic acid in the umbu-cajá FP (73.92%) and the lowest for gentisic acid in the mangaba FP (8.71%). Siriguela and umbu-cajá FP dialysates presented the highest capacity for the capture of the radical 2,2'-diphenyl-2-picrylhydrazyl hydrate, whereas the mangaba FP dialysate demonstrated the highest iron reducing capacity.