One such prominent phenolic acid is gallic acid which is found in a wide variety of vegetables,fruits, tea, coffee and wine. It occurs in plants in the form of free acids,
esters, catechin derivatives and hydrolysable tannins. It also occur as methylated gallic acids e.g., syringic acid or galloyl conjugates of catechin derivatives, i.e., flanvan-3-ols, or polygalloyl esters of glucose,quinic acid or glycerol [3,4].