InVivo Release of 14C-Labelled Phenolic Groups from Intact Dietary Spinach Cell Walls During Passage Through the Rat Intestine

Feruloyl and p-coumaroyl groups in spinach cell walls (CW) were labelled using [14C]cinnamic acid and fed to rats. In the caecum and colon, ferulic acid (FA) and p-coumaric acid (PCA) were released from the CW. Few feruloyl or coumaroyl groups remained in the CW to be excreted in faeces, and thus the presence of simple phenol–sugar esters provided little protection of the polysaccharides to enzymic attack. Some oxidatively coupled phenols were also released but a portion remained in the CW. The oxidatively coupled phenols accumulated in the gut whereas the FA and PCA were absorbed by the rat. Thus enzyme-resistant fragments, containing oxidatively coupled phenols (and possibly sugar residues), may survive microbial attack by rat intestinal bacteria.