British Journal of Nutrition

Full Papers

Flavanol monomer-induced changes to the human faecal microflora

Xenofon Tzounisa1, Jelena Vulevica2, Gunter G. C. Kuhnlea3, Trevor Georgea1, Jadwiga Leonczaka4, Glenn R. Gibsona2, Catherine Kwik-Uribea4 and Jeremy P. E. Spencera1 c1

a1 Molecular Nutrition Group, School of Chemistry, Food and Pharmacy, University of Reading, Reading RG2 6AP, UK

a2 Food and Microbial Sciences Unit, School of Chemistry, Food and Pharmacy, University of Reading, Reading, RG2 6AP, UK

a3 MRC Dunn Human Nutrition Unit, MRC/Wellcome Trust Building, Cambridge CB2 2XY, UK

a4 Analytical and Applied Sciences Group, Mars, Incorporated, 800 High Street, Hackettstown, NJ 07840, USA

Abstract

We have investigated the bacterial-dependent metabolism of ( − )-epicatechin and (+)-catechin using a pH-controlled, stirred, batch-culture fermentation system reflective of the distal region of the human large intestine. Incubation of ( − )-epicatechin or (+)-catechin (150 mg/l or 1000 mg/l) with faecal bacteria, led to the generation of 5-(3′,4′-dihydroxyphenyl)-γ-valerolactone, 5-phenyl-γ-valerolactone and phenylpropionic acid. However, the formation of these metabolites from (+)-catechin required its initial conversion to (+)-epicatechin. The metabolism of both flavanols occurred in the presence of favourable carbon sources, notably sucrose and the prebiotic fructo-oligosaccharides, indicating that bacterial utilisation of flavanols also occurs when preferential energy sources are available. (+)-Catechin incubation affected the growth of select microflora, resulting in a statistically significant increase in the growth of the Clostridium coccoidesEubacterium rectale group, Bifidobacterium spp. and Escherichia coli, as well as a significant inhibitory effect on the growth of the C. histolyticum group. In contrast, the effect of ( − )-epicatechin was less profound, only significantly increasing the growth of the C. coccoidesEubacterium rectale group. These potential prebiotic effects for both (+)-catechin and ( − )-epicatechin were most notable at the lower concentration of 150 mg/l. As both ( − )-epicatechin and (+)-catechin were converted to the same metabolites, the more dramatic change in the growth of distinct microfloral populations produced by (+)-catechin incubation may be linked to the bacterial conversion of (+)-catechin to (+)-epicatechin. Together these data suggest that the consumption of flavanol-rich foods may support gut health through their ability to exert prebiotic actions.

(Received July 02 2007)

(Revised August 29 2007)

(Accepted September 25 2007)

Correspondence:

c1 Corresponding author: Dr Jeremy P. E. Spencer, fax +44 118 931 0080, email j.p.e.spencer@reading.ac.uk

Footnotes

Abbreviations: FISH, fluorescent in situ hybridisation; FOS, fructo-oligosaccharides; FRAP, ferric-reducing antioxidant power

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