3-4-dihydroxyphenylpropionic-acid and 3-hydroxybenzeneacetic-acid

Oligomers and polymers of flavan-3-ols (proanthocyanidins) are very abundant in the Mediterranean diet, but are poorly absorbed. However, when these polyphenols reach the colon, they are metabolised by the intestinal microbiota into various phenolic acids, including phenylpropionic, phenylacetic and benzoic acid derivatives. Since the biological properties of these metabolites are not completely known, in the present study, we investigated the effect of the following microbial phenolic metabolites: 3,4-dihydroxyphenylpropionic acid (3,4-DHPPA), 3-hydroxyphenylpropionic acid, 3,4-dihydroxyphenylacetic acid (3,4-DHPAA), 3-hydroxyphenylacetic acid, 4-hydroxybenzoic acid and 4-hydroxyhippuric acid (4-HHA), on modulation of the production of the main pro-inflammatory cytokines (TNF-alpha, IL-1beta and IL-6). The production of these cytokines by lipopolysaccharide (LPS)-stimulated peripheral blood mononuclear cells (PBMC) pre-treated with the phenolic metabolites was studied in six healthy volunteers. With the exception of 4-HHA for TNF-alpha secretion, only the dihydroxylated compounds, 3,4-DHPPA and 3,4-DHPAA, significantly inhibited the secretion of these pro-inflammatory cytokines in LPS-stimulated PBMC. Mean inhibition of the secretion of TNF-alpha by 3,4-DHPPA and 3,4-DHPAA was 84.9 and 86.4 %, respectively. The concentrations of IL-6 in the culture supernatant were reduced by 88.8 and 92.3 % with 3,4-DHPPA and 3,4-DHPAA pre-treatment, respectively. Finally, inhibition was slightly higher for IL-1beta, 93.1 % by 3,4-DHPPA and 97.9 % by 3,4-DHPAA. These results indicate that dihydroxylated phenolic acids derived from microbial metabolism present marked anti-inflammatory properties, providing additional information about the health benefits of dietary polyphenols and their potential value as therapeutic agents.

Topics: 3,4-Dihydroxyphenylacetic Acid; Adult; Anti-Inflammatory Agents; Bacteria; Caffeic Acids; Cells, Cultured; Cytokines; Depression, Chemical; Female; Flavonoids; Hippurates; Humans; Interleukin-1beta; Interleukin-6; Leukocytes, Mononuclear; Lipopolysaccharides; Male; Parabens; Phenols; Phenylacetates; Polyphenols; Propionates; Tumor Necrosis Factor-alpha

Phenolic compounds are not completely absorbed in the small intestine and so enter the colon, where they might exert physiological effects. To identify phenolics that are present in normal human colon, fecal water was prepared from 5 free-living volunteers with no dietary restrictions and analyzed by gas chromatography-mass spectrometry. Daily measurements were also performed on a single individual to examine the variation more closely. Levels of polyphenols were variable between individuals. Naringenin and quercetin had mean concentrations of 1.20 and 0.63 microM. All other flavonoids examined were present < or =0.17 microM. Simple phenolic and other aromatic acids were present at much higher concentrations. The major components were phenylacetic acid, 479 microM; 3-phenylpropionic acid, 166 microM; 3-(4-hydroxy)-phenylpropionic acid, 68 microM; 3,4-dihydroxycinnamic acid, 52 microM; benzoic acid, 51 microM; 3-hydroxyphenylacetic acid, 46 microM; and 4-hydroxyphenylacetic acid, 19 microM. Other phenolic acids ranged from 0.04 to 7 microM. Decreased dietary phenolic intake caused a decrease in polyphenol and monophenolic acid concentration in fecal water 24 h later. This study is the first to measure the range of aromatic compounds in human fecal water and demonstrates that phenolic acid concentrations are high. The biological effects of phenolics may play an important role in colon function.

Topics: Adult; Benzoic Acid; Caffeic Acids; Colon; Diet; Dose-Response Relationship, Drug; Feces; Flavanones; Flavonoids; Free Radicals; Gas Chromatography-Mass Spectrometry; Humans; Intestine, Small; Male; Models, Chemical; Phenol; Phenols; Phenylacetates; Phenylpropionates; Polyphenols; Quercetin; Time Factors