Analysis of condensed tannins: a review

Plant condensed tannins (proanthocyanidins, PAs) have both positive and neg ative effects on feed digestibility and animal performance, depending both on the quantity and biological activity of the tannins that are present. In this review, the chemistry and analysis of condensed tannins (PAs) are exa mined. Our first focus is on the complexity of the structures of condensed tannins and our second emphasis is on the analytical methods used to evalua te tannins. The section on methods is subdivided into a discussion of metho ds to determine the amount of condensed tannins or total phenolics in a sam ple and a section on methods to measure biological activity. The methods to measure reactivity include assays involving protein binding and precipitat ion, as well as those that involve enzymatic and microbial inhibition. The last section of the paper discusses structure-activity relationships and pr ovides information on how to select appropriate assays for measurement of t he quantity and activity of condensed tannins. (C) 2001 Elsevier Science B. V. All rights reserved.