RELEASE OF COVALENTLY BOUND FERULIC ACID FROM FIBER IN THE HUMAN COLON

The action of wheat bran as a potential colon anticarcinogen is relate d partly to its low fermentability in the large intestine. Phenolic ac ids are highly bioactive components and also limit degradability of wh eat bran in ruminants. Therefore, the solubilization of covalently bou nd phenolic acids during the fermentation of wheat bran in a human mod el colon was examined. Phenolics were only partially and relatively sl owly solubilized from wheat bran, but were rapidly and fully solubiliz ed from sugarbeet fiber; the levels of free ferulic acid in fermentati on liquors remained very low and did not reflect the amounts solubiliz ed from fiber sources. Xylanase and ferulic acid esterase activities w ere shown to be present. The released ferulic acid did not appear to b ind noncovalently to the residual wheat bran fiber. Thus: fermentation in the gut alters the partition of esterified phenolic acids from the insoluble residue and the soluble fraction, where microbial ferulic a cid esterase(s) can potentially yield free ferulic acid.