It is well known that ferulic acid units are found esterified with
arabinoxylan units in wheat bran. The results indicated that some of
these units might be naturally in their radical forms. However, green
tea catechins are very effective antioxidant agents on their regenerative
modification. The fact that the different efficiency of the soluble antioxidants
assayed in the present work against the insoluble bound antioxidants
of wheat bran might be due to the different redox reducing
potentials of each soluble antioxidant with respect to that of the
reacting insoluble dietary fiber. According to the mechanismmentioned
above, when hydrogen donating substances like free catechins are
available in the medium, they will come into contact with bound
radicals and rapidly regenerate them by either giving one of their
electrons/hydrogen atoms, becoming radical themselves or constituting
a covalent bond with them. In this type of interaction, the resulting insoluble
fiber material would have an increased total antioxidant capacity
as revealed by the results of present study. It is very important to
taken this into account for the antioxidant effect of the insoluble dietary
fibers when interacting with soluble antioxidants of meals into the gut
and colon, where insoluble fibers like those of wheat bran can remain
up to 24 hwithin them. This information can easily be adapted to develop
new functional dietary fiber products with improved bioavailability.
In addition, functional dietary programs based on the interaction mechanism
of soluble and bound antioxidants can be designed for special
needs.