GC/MS analysis of microbial metabolites from flavanols in an in vitro human colon model

Dietary phenolic compounds are plant derived secondary metabolites, which can be divided into flavonoids, phenolic acids, stilbenes, tannins and lignans. Catechins can be found as monomers or in condensed forms as proanthocyanidins (PA). Pure (+)-catechin, (-)-epicatechin and isolated PA fractions with different chain lengths were fermented with pooled human fecal microbiota in strictly anaerobic conditions. GC/MS analytical method was developed for the analysis of microbial metabolites. We will describe a GC/MS analytical method and the preceding sample preparation steps for the analysis of 11 microbial metabolites of (+)–catechin and (-)-epicatechin. The compounds include e.g. hydroxyphenyl propionic and acetic acid derivatives. The sample preparation steps include sample extraction (wet or dry) with ethyl acetate and silylation with MSTFA. The fermentation and calibration samples are run in SIM mode and quantified using an internal standard. Different extraction methods and chromatographical methods are compared.