Release of Covalently Bound Ferulic Acid from Fiber in the Human Colon
Received for review June 18, 1996. Revised manuscript
received November 20, 1996. Accepted November 22, 1996. Abstract: The action of wheat bran as a potential colon anticarcinogen is related
partly to its low fermentability
in the large intestine. Phenolic acids are highly bioactive
components and also limit degradability
of wheat bran in ruminants. Therefore, the solubilization of
covalently bound phenolic acids during
the fermentation of wheat bran in a human model colon was examined.
Phenolics were only partially
and relatively slowly solubilized from wheat bran, but were rapidly and
fully solubilized from
sugarbeet fiber; the levels of free ferulic acid in fermentation
liquors remained very low and did not
reflect the amounts solubilized from fiber sources. Xylanase and
ferulic acid esterase activities
were shown to be present. The released ferulic acid did not appear
to bind 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 acid esterase(s)
can potentially yield free ferulic acid.
Keywords: Ferulic acid; phenolic acids; plant cell walls; fiber; wheat
bran; sugarbeet pulp; colon
fermentation; phenolic antioxidants; esterases; xylanase
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