Characterization of microbial metabolism of Syrah grape products in an in vitro colon model using targeted and non-targeted analytical approaches.
OBJECTIVE
Syrah red grapes are used in the production of tannin-rich red wines. Tannins are high molecular weight molecules, proanthocyanidins (PAs), and poorly absorbed in the upper intestine. In this study, gut microbial metabolism of Syrah grape phenolic compounds was investigated.


METHODS
Syrah grape pericarp was subjected to an enzymatic in vitro digestion model, and red wine and grape skin PA fraction were prepared. Microbial conversion was screened using an in vitro colon model with faecal microbiota, by measurement of short-chain fatty acids by gas chromatography (GC) and microbial phenolic metabolites using GC with mass detection (GC-MS). Red wine metabolites were further profiled using two-dimensional GC mass spectrometry (GCxGC-TOFMS). In addition, the effect of PA structure and dose on conversion efficiency was investigated by GC-MS.


RESULTS
Red wine exhibited a higher degree of C1-C3 phenolic acid formation than PA fraction or grape pericarp powders. Hydroxyphenyl valeric acid (flavanols and PAs as precursors) and 3,5-dimethoxy-4-hydroxybenzoic acid (anthocyanin as a precursor) were identified from the red wine metabolite profile. In the absence of native grape pericarp or red wine matrix, the isolated PAs were found to be effective in the dose-dependent inhibition of microbial conversions and short-chain fatty acid formation.


CONCLUSIONS
Metabolite profiling was complementary to targeted analysis. The identified metabolites had biological relevance, because the structures of the metabolites resembled fragments of their grape phenolic precursors or were in agreement with literature data.
VTT Technical Research Centre of Finland, Espoo, Finland. anna-marja.aura@vtt.fi
Anna-Marja
AM
Aura
Ismo
I
Mattila
Tuulia
T
Hyötyläinen
Peddinti
P
Gopalacharyulu
Veronique
V
Cheynier
Jean-Marc
JM
Souquet
Magali
M
Bes
Carine
C
Le Bourvellec
Sylvain
S
Guyot
Matej
M
Orešič
D003106:Colon / Q000378:metabolism* / Q000382:microbiology; D004063:Digestion; D005232:Fatty Acids, Volatile / Q000032:analysis; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D062385:Hydroxybenzoates / Q000032:analysis; D055442:Metabolome; D054892:Metagenome; D008954:Models, Biological; D028321:Plant Preparations; D059808:Polyphenols / Q000032:analysis; D044945:Proanthocyanidins / Q000032:analysis; D027843:Vitis / Q000737:chemistry*; D014920:Wine / Q000032:analysis
D005232:Fatty Acids, Volatile; D062385:Hydroxybenzoates; D028321:Plant Preparations; D059808:Polyphenols; D044945:Proanthocyanidins; C017616:phenolic acid