Simulated gastrointestinal digestion of cranberry polyphenols under dynamic conditions. Impact on antiadhesive activity against uropathogenic bacteria.

This study is the first dynamic simulation of gastrointestinal digestion of cranberry polyphenols [1 g cranberry extract per day (206.2 mg polyphenols) for 18 days]. Samples from the simulated ascending, transverse, and descending colon of the dynamic gastrointestinal simulator simgi® were analyzed. Results showed that 67% of the total cranberry polyphenols were recovered after simulated gastrointestinal digestion. Specifically, benzoic acids, hydroxycinnamic acids, phenylpropionic acids, phenylacetic acids, and simple phenols were identified. Cranberry feeding modified colonic microbiota composition of Enterococcaceae population significantly. However, increments in microbial-derived short-chain fatty acids, particularly in butyric acid, were observed. Finally, the simgi® effluent during cranberry feeding showed significant antiadhesive activity against uropathogenic Escherichia coli (13.7 ± 1.59 % of inhibition). Understanding the role that gut microbiota plays in cranberry metabolism could help to elucidate its interaction with the human body and explain cranberry protective effects against urinary tract infections.

In Vitro Colonic Fermentation of Saponin-Rich Extracts from Quinoa, Lentil, and Fenugreek. Effect on Sapogenins Yield and Human Gut Microbiota.

In vitro colonic fermentation of saponin-rich extracts from quinoa, lentil, and fenugreek was performed. Production of sapogenins by human fecal microbiota and the impact of extracts on representative intestinal bacterial groups were evaluated. The main sapogenins were found after fermentation (soyasapogenol B for lentil; oleanolic acid, hederagenin, phytolaccagenic acid, and serjanic acid for quinoa; and sarsasapogenin, diosgenin, and neotigogenin acetate for fenugreek). Interindividual differences were observed, but the highest production of sapogenins corresponded to quinoa (90 µg/mL) and fenugreek (70 µg/mL) extracts, being minor for lentil (4 µg/mL). Lentil and quinoa extracts showed a general antimicrobial effect, mainly on lactic acid bacteria and Lactobacillus spp. Significant increases of Bifidobacterium spp. and Lactobacillus spp. were observed for fenugreek in one volunteer. Thus, the transformation of saponin-rich extracts of quinoa, lentil, and fenugreek to sapogenins by human gut microbiota is demonstrated, exhibiting a modulatory effect on the growth of selected intestinal bacteria.

Behaviour of citrus pectin during its gastrointestinal digestion and fermentation in a dynamic simulator (simgi®).

The behaviour of citrus pectin during digestion and its potential prebiotic properties were examined using a Dynamic Gastrointestinal Simulator (simgi®) model for the human gut, which simulates processes in the stomach, small intestine, ascending, transverse and descending colon. A remarkable non-digestibility of pectin in the upper gastrointestinal tract was observed by HPLC-ELSD analysis, where ∼88% of citrus pectin remained intact during its transit through the stomach and small intestine. Fermentation of pectin stimulated the growth of beneficial bacteria such as Bifidobacterium spp, Bacteroides spp and Faecalobacterium prausnitzii. High increases of short-chain fatty acids (SCFA) were observed, especially in acetate and butyrate concentration due to direct fermentation of pectin or by cross-feeding interaction between bacteria. This is the first study on the digestibility and fermentation of pectin carried out in a complex dynamic gastrointestinal simulator, being of special relevance the results obtained for F. prausnitzii.

Chemical characterization and in vitro colonic fermentation of grape pomace extracts.

BACKGROUND: Currently, there is growing interest in extracts derived from winery by-products because of their beneficial health properties, which are associated with the presence of bioactive compounds. In this paper, we have carried out the chemical characterization and in vitro colonic fermentation of four grape pomace (GP) extracts rich in polyphenols and dietary fibre. RESULT: Firstly, phenolic and dietary fibre composition of the GP extracts was determined. The highest individual phenolic concentrations corresponded to gallic and ellagic acids, followed by catechins and flavonols. The non-digestible fibre fraction ranged from 66% to 83% of the GP extracts, which indicated that they mainly contained non-digestible cell wall components. Secondly, when GP extracts were subjected to fermentation by faecal microbiota, a total of 16 bacterial phenolic metabolites were found in the fermented samples, confirming that polyphenols contained in the GP extracts were metabolized to different active metabolites by microbiota. In addition, the GP extracts tended to promote the growth of intestinal microbiota, although it was only significant for the Enterococcus group. CONCLUSION: These findings, together with other information available in the literature, support the high added value of products obtained from winery by-products. © 2016 Society of Chemical Industry.

Susceptibility and tolerance of human gut culturable aerobic microbiota to wine polyphenols.

Diet is one of the main factors that could affect quantitatively and qualitatively the stability of the gut microbiota. Polyphenols are abundantly present in the human diet and have an antimicrobial effect inducing selective changes in the microbiota composition, with potential beneficial effects for the human health. Our aim was to determine the human gut microbiota susceptibility toward wine polyphenols. Susceptibility to two commercial wine phenolic extracts (Vitaflavan(®) and Provinols™) was determined in isolates from fecal samples from 36 gastrointestinal healthy volunteers. To select the polyphenol-resistant isolates, feces were seeded in plates containing 1 mg/ml of phenolic extract. The minimal inhibitory concentration to polyphenols in the collected isolates was assessed by the agar dilution method. Overall results showed that Gram-negative isolates are most tolerant to the presence of both grape seed and red wine extracts. Furthermore, we purified to homogeneity the phenolic fractions by high-performance liquid chromatography (HPLC) to determine their antimicrobial effect and their influence on bacterial growth in four selected ATCC strains using the BioScreen apparatus. Results showed that the antimicrobial activity of the wine polyphenols is the result of the interaction of both the flavan-3-ol type and the bacteria. Bacterial Intraspecies differences in the phenolic susceptibility suggest the existence of polyphenol-resistant mechanisms that are uncharacterized as yet.

In vitro fermentation of grape seed flavan-3-ol fractions by human faecal microbiota: changes in microbial groups and phenolic metabolites.

With the aim of investigating the potential of flavan-3-ols to influence the growth of intestinal bacterial groups, we have carried out the in vitro fermentation, with human faecal microbiota, of two purified fractions from grape seed extract (GSE): GSE-M (70% monomers and 28% procyanidins) and GSE-O (21% monomers and 78% procyanidins). Samples were collected at 0, 5, 10, 24, 30 and 48 h of fermentation for bacterial enumeration by fluorescent in situ hybridization and for analysis of phenolic metabolites. Both GSE-M and GSE-O fractions promoted growth of Lactobacillus/Enterococcus and decrease in the Clostridium histolyticum group during fermentation, although the effects were only statistically significant with GSE-M for Lactobacillus/Enterococcus (at 5 and 10 h of fermentation) and GSE-O for C. histolyticum (at 10 h of fermentation). Main changes in polyphenol catabolism also occurred during the first 10 h of fermentation; however, no significant correlation coefficients (P > 0.05) were found between changes in microbial populations and precursor flavan-3-ols or microbial metabolites. Together, these data suggest that the flavan-3-ol profile of a particular food source could affect the microbiota composition and its catabolic activity, inducing changes that could in turn affect the bioavailability and potential bioactivity of these compounds.