Total Tannin Content

Tannins are high molecular weight phenolic compounds having the ability to precipitate proteins. They are class of secondary metabolites that widely distributed in many plants. Two types of tannins are commonly found in natural products: hydrolysable and condensed tannins. Hydrolysable tannins are complex monomeric or oligomeric polyesters of phenolic acids (gallic or ellagic) with D-glucose or related sugars. Hydrolysable tannins include gallo-, ellagi-tannins and tannic acid. While condensed tannins, also named procyanidins, are dimers to polymers of flava-3-ol (such as catechin). Examples of condensed tannins are procyanidin A2 and B2.

Available Tests:

• Determination of total tannins

Total tannins can be determined using the FeCl3/K4[Fe(CN)6] method. The produced color can be measured quantitatively and represented as tannic acid equivalents.

• Determination of procyanidin content

Procyanidins can be determined using the method of Vanillin-HCl assay. In acidic condition, vanillin reacts with catechins to yield a red colored product which can be measured colorimetrically and represented as catechin equivalents.

Delivered Data:

A calibration curve of standard compound (catechin and tannic acid in case of procyanidins and total tannins, respectively).

Data are presented as catechin and tannic acid equivalents per/g extract.