Methods for Determination of Condensed and Hydrolyzable Tannins

Tannins are natural products which are characterized by their phenolic nature and their ability to precipitate protein. Their diverse biological effects, and their common occurrence in plants used to make foods, beverages, herbal medicines, and animal feeds, have created widespread interest in methods for the analysis of tannins. However, their chemical complexity and diversity impose constraints upon the application of many of the analytical methods that have been developed. After briefly reviewing the chemistry of tannins, we describe some of the methods available for analysis of tannins, and outline the limitations of those methods. The discussion of each method emphasizes the utility of the method for analysis of mixtures of tannin, like those found in many foods. A procedure for preparative scale purification of a standard gallotannin, pentagalloyl glucose, is included. A new method for simultaneous determination of condensed and hydrolyzable tannins is summarized.