3.3. Bound phenolic acids and flavonoid content in mango
peel dietary fibre
Phenolic acids may form both ester and ether linkages owing
to their bifunctional nature through reactions involving their
carboxylic and hydroxyl groups, respectively. This allows phenolic acids to form cross-links with cell wall macromolecules
such as polysaccharides, proteins or fatty acids (Yu, Vasanthan, & Tamelli, 2001). Cross-linking of lignin components
via phenolic acids appears to have a profound effect on the
growth of cell wall and its mechanical properties and biodegradability. Such cross-linked phenolic fractions are not
extractable in aqueous organic solvents, and therefore, can
be referred as insoluble bound phenolics. Insoluble bound
phenolic acids may be released by alkali, acid or enzymatic
treatment of sample prior to extraction, for isolation and
identification. In the present study, alkaline hydrolysis was
adopted to extract the phenolic acids.