There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Flavonoids are a group of phytochemicals that have shown numerous health effects and have therefore been studied extensively. Of the six common food flavonoid classes, flavonols are distributed ubiquitously among different plant foods whereas appreciable amounts of isoflavones are found in leguminous plant-based foods. Flavonoids have shown promising health promoting effects in human cell culture, experimental animal and human clinical studies. They have shown antioxidant, hypocholesterolemic, anti-inflammatory effects as well as ability to modulate cell signaling and gene expression related disease development. Low bioavailability of flavonoids has been a concern as it can limit or even hinder their health effects. Therefore, attempts to improve their bioavailability in order to improve the efficacy of flavonoids are being studied. Further investigations on bioavailability are warranted as it is a determining factor for flavonoid biological activity.

Flavonoid bioavailability and attempts for bioavailability enhancement.

A review on anticancer potential of bioactive heterocycle quinoline.

As of late, polyphenols have increasingly interested the scientific community due to their proposed health benefits. Much of this attention has focused on their bioavailability. Polyphenol–gut microbiota interactions should be considered to understand their biological functions. The dichotomy between the biotransformation of polyphenols into their metabolites by gut microbiota and the modulation of gut microbiota composition by polyphenols contributes to positive health outcomes. Although there are many studies on the in vivo bioavailability of polyphenols, the mutual relationship between polyphenols and gut microbiota is not fully understood. This review focuses on the biotransformation of polyphenols by gut microbiota, modulation of gut microbiota by polyphenols, and the effects of these two-way mutual interactions on polyphenol bioavailability, and ultimately, human health.

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The Reciprocal Interactions between Polyphenols and Gut Microbiota and Effects on Bioaccessibility

Anti-inflammatory effects of flavonoids.

Bioavailability of anthocyanins and derivatives

Anthocyanins are naturally occurring compounds abundant in the human diet. Evidence has accumulated regarding the positive association of their intake with healthy biological effects. The microbiota has just been started to be considered as a metabolic organ, hence contributing to the metabolism of phenolic compounds and, consequently, to their bioavailability and the biological effects displayed by them. This review aimed to compile information regarding interaction of anthocyanins with the microbiota, from two perspectives: (i) identification of their colonic metabolites as potential bioactive molecules and (ii) their role as prebiotic agents. These perspectives are key points in anthocyanin metabolomics. Several metabolites have been identified after anthocyanin consumption with potential health benefits, in particular phenolic acids and simple phenols. On the other hand, microbiota modulation is closely related to several physiological impairments, and its modulation has been considered as a possible mechanism by which phenolic compounds may exert their effect.

Interplay between anthocyanins and gut microbiota.

Wine, and particularly red wine, is a beverage with a great chemical complexity that is in continuous evolution. Chemically, wine is a hydroalcoholic solution (~78% water) that comprises a wide variety of chemical components, including aldehydes, esters, ketones, lipids, minerals, organic acids, phenolics, soluble proteins, sugars and vitamins. Flavonoids constitute a major group of polyphenolic compounds which are directly associated with the organoleptic and health-promoting properties of red wine. However, due to the insufficient epidemiological and in vivo evidences on this subject, the presence of a high number of variables such as human age, metabolism, the presence of alcohol, the complex wine chemistry, and the wide array of in vivo biological effects of these compounds suggest that only cautious conclusions may be drawn from studies focusing on the direct effect of wine and any specific health issue. Nevertheless, there are several reports on the health protective properties of wine phenolics for several diseases such as cardiovascular diseases, some cancers, obesity, neurodegenerative diseases, diabetes, allergies and osteoporosis. The different interactions that wine flavonoids may have with key biological targets are crucial for some of these health-promoting effects. The interaction between some wine flavonoids and some specific enzymes are one example. The way wine flavonoids may be absorbed and metabolized could interfere with their bioavailability and therefore in their health-promoting effect. Hence, some reports have focused on flavonoids absorption, metabolism, microbiota effect and overall on flavonoids bioavailability. This review summarizes some of these major issues which are directly related to the potential health-promoting effects of wine flavonoids. Reports related to flavonoids and health highlight some relevant scientific information. However, there is still a gap between the knowledge of wine flavonoids bioavailability and their health-promoting effects. More in vivo results as well as studies focused on flavonoid metabolites are still required. Moreover, it is also necessary to better understand how biological interactions (with microbiota and cells, enzymes or general biological systems) could interfere with flavonoid bioavailability.

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Wine Flavonoids in Health and Disease Prevention

Flavonoid metabolites transport across a human BBB model.

Background Anthocyanins are a major class of phenolic compounds present in red grapes and red wine. They have been reported to possess multiple health-promoting properties. However, the bioavailability of anthocyanins has been reported to be extremely low. In order to better associate anthocyanin consumption to any health-promoting properties, it is very important to understand how grape and wine anthocyanins are digested and metabolized through the gastrointestinal tract and how anthocyanins and their metabolites are absorbed. Scope and approach This review focuses on the digestion and absorption of grapes and wine anthocyanins through the gastrointestinal tract, including oral cavity, stomach and intestinal tract. Moreover, we discussed the major factors that could affect the digestion and metabolism of anthocyanins. Key findings and conclusions In the oral cavity, the pH condition and enzymes secreted from bacteria may lead to the hydrolysis of anthocyanins to phenolic acids or the corresponding aglycones. However, anthocyanins are relatively stable and can be absorbed in the stomach with only a small portion being hydrolyzed. The intestine is the main site for the metabolism and absorption of anthocyanins where microbiota and alkaline condition could catabolize anthocyanins into small molecular phenolic acids and aldehydes. Both anthocyanins and their degraded products can be transported through the intestinal epithelium via passive diffusion or active transporters. Active transporters include hexose transporter, ATP-binding cassette transporters and monocarboxylic acid transporters. In conclusion, the anthocyanins can exert their health benefits not only via their intact compounds but also via degraded products/metabolites. However, further studies are still required to explore in detail the mechanism of digestion and absorption of anthocyanins in red grapes and wine.

Iva Fernandes

Papers

Bioavailability of anthocyanins and derivatives

Interplay between anthocyanins and gut microbiota.

Wine Flavonoids in Health and Disease Prevention

Flavonoid metabolites transport across a human BBB model.

Digestion and absorption of red grape and wine anthocyanins through the gastrointestinal tract.