Polyphenols and bioavailability: an update

Abstract

Based on many cell culture, animal and human studies, it is well known that the most challenge issue for developing polyphenolics as chemoprevention or anti-diabtetic agents is the low oral bioavailability, which may be the major reason relating to its ambiguous therapeutic effects and large inter-individual variations in clinical trials. This review intends to highlight the unscientific evaluation on the basis of the published data regarding in vitro bioactivity of polyphenols, which may sometimes mislead the researchers and to conclude that: first, bio-accessibilities values obtained in the studies for polyphenols should be highly reconsidered in accordance with the abundant newly identified circulating and excreted metabolites, with a particular attention to colonic metabolic products which are obviously contributing much more than expected to their absorptions; second, it is phenolic metabolites, which are formed in the small intestine and hepatic cells,low molecular weight catabolic products of the colonic microflora to travel around the human body in the circulatory system or reach body tissues to elicit bioactive effects. It is concluded that better performed in vivo intervention and in vitro mechanistic studies are needed to fully understand how these molecules interact with human physiological and pathological processes.

Polyphenols: A concise overview on the chemistry, occurrence, and human health

“…Flavonoids derived from the aromatic amino acids, phenylalanine, and tyrosine are C15 compounds arranged in three rings (C6-C3-C6) (Vermerris & Nicholson, 2008); the degree and pattern of hydroxylation, prenylation, alkalization, or glycosylation reactions modify the primary structure of the molecule (Khoddami et al, 2013). The substitution of chemical groups in the flavonoid structures is correlated to the corresponding biological and/or chemical properties and bioavailability (Cermak et al, 2009;Teng & Chen, 2019). Figure 2 shows the chemical structures of molecules belonging to flavanones, that is, hesperetin, naringenin, and eriodictyol.…”

The mechanism(s) of action of antioxidants: From scavenging reactive oxygen/nitrogen species to redox signaling and the generation of bioactive secondary metabolites

“…Microbial metabolism frequently leads to a variety of smaller fragments, including simple phenolic acids, phloroglucinol derivatives, etc. Detailed reviews on this subject have recently been published by others . The following sub‐sections attempt to provide an overview on the known Phase I and Phase II metabolic transformations of curcuminoids ( 1 ‐ 3 ), resveratrol ( 4 ), a set of methyl‐hydroxycinnamates ( 5 ‐ 7 ), secoisolariciresinol ( 8 ), and luteolin ( 9 ), and on related pharmacological consequences.…”

“…These compounds may likely form through free radical scavenging this subject have recently been published by others. 13,[49][50][51][52] The following sub-sections attempt to provide an overview on the known Phase I and Phase II metabolic transformations of curcuminoids (1-3), resveratrol (4), a set of methyl-hydroxycinnamates (5-7), secoisolariciresinol (8), and luteolin (9), and on related pharmacological consequences.…”

“…Moreover, many dietary antioxidants undergo extensive metabolism; those that are not absorbed in the small intestines can also suffer fragmentation into smaller compounds by gut microbiota. This certainly leads to a situation where the activity observed in vivo is necessarily a superposition of the effects of these metabolites on several possible targets …”

“…This certainly leads to a situation where the activity observed in vivo is necessarily a superposition of the effects of these metabolites on several possible targets. 12,13 This paper provides a brief summary on the various mechanisms influenced by the activity of small-molecule antioxidants. A set of dietary phenolic compounds including curcuminoids, a stilbene, hydroxycinnamic acid derivatives, a lignan, and a flavonoid are discussed in detail.…”