In Vitro Bioconversion of Polyphenols from Black Tea and Red Wine/Grape Juice by Human Intestinal Microbiota Displays Strong Interindividual Variability

Abstract

These authors equally contributed to the manuscript.Dietary polyphenols in tea and wine have been associated with beneficial health effects. After ingestion, most polyphenols are metabolized by the colonic microbiota. The current study aimed at exploring the interindividual variation of gut microbial polyphenol bioconversion from 10 healthy human subjects. In vitro fecal batch fermentations simulating conditions in the distal colon were performed using polyphenols from black tea and a mixture of red wine and grape juice. Microbial bioconversion was monitored by NMR-and GC-MS-based profiling of diverse metabolites and phenolics. The complex polyphenol mixtures were degraded to a limited number of key metabolites. Each subject displayed a specific metabolite profile differing in composition and time courses as well as levels of these metabolites. Moreover, clear differences depending on the polyphenol sources were observed. In conclusion, varying metabolite pathways among individuals result in different metabolome profiles and therefore related health effects are hypothesized to differ between subjects.

Role of the small intestine, colon and microbiota in determining the metabolic fate of polyphenols

“…were applied to the in vitro catabolism of black tea or a mixture of red wine and grape juice considerable variation was observed, each individual's microbiota producing a distinct catabolite profile [89]. Interestingly, all 10 microbiota were more efficient at producing 3-(3 -hydroxyphenyl) propionic acid from red wine than from black tea, whereas the yield of 3 -hydroxyphenylacetic acid was much greater from black tea than red wine.…”

“…2 and 5). Human studies in vivo and gut microbiota-fermentation studies have demonstrated that at least some of these C 6 -C 1 and possibly C 6 -C 2 phenolic acids can be decarboxylated yielding the corresponding phenols (C 6 ) or methyl-phenols (C 6 -C 1 ) [84,[86][87][88][89][90], respectively. Phloroglucinol can also be formed from chalcones and dihydrochalcones [91,92], and at least certain rumen microorganisms can reduce this to non-aromatic dihydrophloroglucinol [93,94].…”

The urinary phenolic acid profile varies between younger and older adults after a polyphenol-rich meal despite limited differences in in vitro colonic catabolism

“…The phenolic acids consistently seen in urines from both younger and old subjects were BA, MA, 3-OHPAA, HVA, 4-OHMA, 3,4diOHPAA, HA, and 3-OHhippA with 3-OHPAA, HVA, and 3,4diOHPAA, well described rutin metabolites [27,48]. Intermediates (3,4-diOHBA, 3,4-diOHPAA, 3,4-diOHPPA) were detected in variable PAA [59] Younger Blank 3.7 (n = 6/6) 3.0-4.0 15.2 (n = 6/6) 6.0-28.1 66.1 (n = 6/6) 46.8-72.2 Raftiline 2.7 (n = 6/6) 2.9-5.2 8.6 (n = 6/6) 7.4-8.8 6.6 (n = 6/6) 6.9-10.6 Rutin 3.3 (n = 6/6) 2.3-3.9 6.0 (n = 6/6) 3.5-11.3 81.9 (n = 6/6) 44.4-95.5 Rutin + raftiline 4.3 (n = 6/6) 2.5-3. amounts at different time points, but the absence of these phenolic acids at any given point does not simply illustrate capacity, but also the kinetics in flavonol catabolism.…”

“…In older adults (40-50 years old), a higher urinary concentration of phenolic metabolites of anthocyanin such as syringic acid, p-coumaric acid, 4-hydroxybenzoic acid, and homovanillic acid was associated with higher bifidobacteria level (> 4.47 vs. < 1.18 log 10 copies per g faeces) [17]. Research into the bioavailability and metabolism of (poly)phenols, has so far been mostly limited to young adults [21][22][23][24][25][26], and inter-individual factors likely to impact on the outcome measures have rarely been studied in depth [27][28][29][30][31][32][33]. One study, in particular, looked at the effect of ageing on the absorption, metabolism, and excretion of epicatechin in healthy younger and older subjects after the consumption of cocoa flavanols, with little difference observed between subjects; the study did not, however, consider the colonic metabolism of epicatechin, or phenolic acids production [34].…”

The Simulator of the Human Intestinal Microbial Ecosystem (SHIME®)

“…with the onset of isoxanthohumol conversion into 8-prenylnaringenin , or even hours, e.g. with the microbial conversion of tea catechins and wine polyphenols (Gross et al 2010 ).…”