bound phenolic acids (Renger and Steinhart, 2000). The free forms
of phenolic compounds are very rarely present in plants. Majority
of phenolic acids exists in the form of ester, acetal, or ethers and
some of the phenolic acids are linked either to structural compounds
of plants such as protein, dietary fiber or to longer or smaller
organic molecules such as glucose, maleic acid or to other
natural products (Robbins, 2003; Nardini et al., 2004).