Table 2.

The most prevalent dietary polyphenols and their major colonic metabolites.

Polyphenol Class	Metabolites	Bioavailability	References
Anthocyanins	Catechol Glucunoride conjugates Hydroxyhippuric acid Methyl conjugates Propionic acid Protocatechuic acid Pyrogallol Sulphate conjugates Syringic acid Vanillic acid	Absorption: A minor amount of glycosylated anthocyanin product is immediately absorbed in the gut, resulting in maximal plasma concentrations ranging from 14 to 592 nmol/L at 4–5 h after intake (doses: 68–1300 mg). Metabolism: Through glucosidase activity, the gut bacteria hydrolyze anthocyanins. Cleavage of the C3-ring breaks down the aglycones, which are then metabolized into various phenolic and aldehydic components. Excretion: Urinary excretion is estimated to be between 0.03% and 4% of the ingested dosage, with elimination half-lives of 15–3 h.	[92,100,101,102,103]
Phenolic acids	Dihydrocaffeic acid Feruloylglycine Dihydrofeluric acid Hydroxybenzoic acid Vanillic acid Hippuric acid	Absorption: Approximately 30 min after consumption, the maximal plasma concentration level is attained, and this is because its maximum absorption occurs in the small intestine. Metabolism: These chemicals are metabolized and circulated in the body as glucuronate, sulfate, and methylated metabolites with varying degrees of bioactivity. Excretion: Urinary excretions account for roughly 40% of total consumption, with excretion peaking after 8 h.	[92,100,104,105]
Flavonols	Hydroxyphenylacetic derivates Protocatechuric acid Propionic acid	Absorption: Small intestine absorption is poor. Metabolism: The flavonol skeleton is broken down by gut microbiota microbial enzymes, resulting in the production of low-molecular-weight polar metabolites. Excretion: The clearance of epicatechin metabolites relies heavily on urine excretion.	[92,100,106]
Flavan-3-ols and Proanthocyanidins	Benzoic acids Hippuric acids Phenilvalerolactones Phenylacetic acids Phenylpropionic acids Phenylvaleric acids	Absorption: The small intestine absorbs between 8 and 17 percent of monomeric-3-ols. Metabolism: The leftover unabsorbed portion reaches the other end of the large intestine practically intact, and their gut bacteria cause the breakdown of the flavonoid skeleton, producing several low-molecular-mass metabolites.	[19,92,100,107]
Ellagitanninis	Dimethyl-ellagic acid Urolithin A and B Urolithin D	Absorption: Ellagitannins are hydrolyzed in the gastrointestinal lumen after intake, yielding a free form of ellagic acid. Metabolism: The gut microbiota degrades ellagic acid in the large intestine, resulting in a variety of derivative chemicals known as urolithins, all of which have the same nucleus. Urolithins are substantially absorbed and metabolized as glucuronidated and sulfated products by hepatic and intestinal cells.	[92,108,109]
Stilbenes	3,4′-dihydro-trans-stilbene Dihydroresveratrol 3,4′-dihydroxybibenzyl	Absorption: The upper gastrointestinal tract absorbs resveratrol. Metabolism: Enterocytes and hepatocytes both metabolize it, producing glucuronide and sulfate forms.	[92,100,110,111,112,113,114]