Metabolic and Microbial Modulation of the Large Intestine Ecosystem by Non-Absorbed Diet Phenolic Compounds: A Review

Abstract

Phenolic compounds represent a diverse group of phytochemicals whose intake is associated with a wide spectrum of health benefits. As consequence of their low bioavailability, most of them reach the large intestine where, mediated by the action of local microbiota, a series of related microbial metabolites are accumulated. In the present review, gut microbial transformations of non-absorbed phenolic compounds are summarized. Several studies have reached a general consensus that unbalanced diets are associated with undesirable changes in gut metabolism that could be detrimental to intestinal health. In terms of explaining the possible effects of non-absorbed phenolic compounds, we have also gathered information regarded their influence on the local metabolism. For this purpose, a number of issues are discussed. Firstly, we consider the possible implications of phenolic compounds in the metabolism of colonic products, such as short chain fatty acids (SCFA), sterols (cholesterol and bile acids), and microbial products of non-absorbed proteins. Due to their being recognized as affective antioxidant and anti-inflammatory agents, the ability of phenolic compounds to counteract or suppress pro-oxidant and/or pro-inflammatory responses, triggered by bowel diseases, is also presented. The modulation of gut microbiota through dietetic maneuvers including phenolic compounds is also commented on. Although the available data seems to assume positive effects in terms of gut health protection, it is still insufficient for solid conclusions to be extracted, basically due to the lack of human trials to confirm the results obtained by OPEN ACCESSMolecules 2015, 20 17430 the in vitro and animal studies. We consider that more emphasis should be focused on the study of phenolic compounds, particularly in their microbial metabolites, and their power to influence different aspects of gut health.

The role of metabolism (and the microbiome) in defining the clinical efficacy of dietary flavonoids

“…Equol has been shown to be more bioactive than its food precursor daidzein in vitro and in trials (predominantly with the equol-producer phenotype assessed retrospectively), the magnitude of the biological effect was greatly enhanced in participants who produced equol after isoflavone ingestion, which suggested that there is a critical role of the microbiome for health effects (125–127). In general terms, there is emerging literature that describes the diverse and significant impact of flavonoid phenolics and other small molecules that are produced in the large intestine on physiologic processes such as SCFA production and bioavailability, bile acid metabolism, redox and inflammatory status, and associated intestinal, hepatic, and overall systemic functions (128). The production of SCFA is of interest in colonic health, dietary energy extraction, and body-weight regulation (128, 129).…”

“…In general terms, there is emerging literature that describes the diverse and significant impact of flavonoid phenolics and other small molecules that are produced in the large intestine on physiologic processes such as SCFA production and bioavailability, bile acid metabolism, redox and inflammatory status, and associated intestinal, hepatic, and overall systemic functions (128). The production of SCFA is of interest in colonic health, dietary energy extraction, and body-weight regulation (128, 129). Although flavonoid-induced effects on the main SCFAs acetic (C2), propionic (C3), and butyric (C4) acids have been repeatedly shown in in vitro fermentation systems and in rodent models (128), data from human interventions have been limited and nonconclusive.…”

“…The production of SCFA is of interest in colonic health, dietary energy extraction, and body-weight regulation (128, 129). Although flavonoid-induced effects on the main SCFAs acetic (C2), propionic (C3), and butyric (C4) acids have been repeatedly shown in in vitro fermentation systems and in rodent models (128), data from human interventions have been limited and nonconclusive. For example, in healthy humans, red-wine grape-juice extract, but not grape-juice extract, fed for 4 wk reduced fecal isobutyric acid concentrations (130), whereas Mosele et al (131) reported no impact of 4 wk of pomegranate-juice consumption on total or individual fecal SCFA concentrations.…”

Potential of plant polyphenols to combat oxidative stress and inflammatory processes in farm animals

“…Considering similar effects of polyphenol‐enriched diets in laboratory animals (Larrosa et al., ; Qiao et al., ; Etxeberria et al., ), it can be postulated that a key mechanism of this beneficial effect of polyphenol‐rich diets in pigs is their contribution to gut health by exerting a pre‐biotic activity favouring the growth of beneficial bacteria while inhibiting the growth of pathogenic bacteria. This beneficial modulation of the gut microbiota is known to enhance gut barrier function, decrease the translocation of bacterial components into the circulation and stimulate the host immune system (Mosele et al., ). In line with this, it was reported that the modulation of the colon microbiota by plant polyphenols correlated with reduced levels of systemic inflammatory markers, such as C‐reactive protein, and decreased expression of inflammatory genes in tissues (Axling et al., ; Queipo‐Ortuño et al., ; Moreno‐Indias et al., ).…”

Some Contributions to the Study of Oenological Lactic Acid Bacteria through Their Interaction with Polyphenols

“…and decreased undesirable bacteria such as clostridia after batch culture fermentations [16]. Phenolic compounds contained in a cocoa powder reduced the growth of some members of the genera Staphylococcus and Clostridium, affecting the intestinal microbiota profile [17].…”