Feasibility and application of liquid-liquid extraction combined with gas chromatography-mass spectrometry for the analysis of phenolic acids from grape polyphenols degraded by human faecal microbiota

► LLE-GC-EI-MS is a suitable method for the characterisation of gut phenolic metabolites. ► Anaerobic incubations of a commercial grape seed extracts with human faeces. ► Gut microbiota prefer flavan-3-ol monomers than procyanidin oligomers. ► Large interindividual differences in the bioconversion rate.