Condensed tannins, acid butanol assay

Several methods have been described in the literature to quantify proanthocyanidins (condensed tannins) however, the most common are the acid-butanol assay and vanillin assay. 

Gessner MO, Steiner D (2005) Acid butanol assay for proanthocyanidins (condensed tannins). In Gra9a MAS, Barlocher F, Gessner MO (eds) Methods to study litter decomposition a practical guide. Springer, Netherlands... 

The proanthocyanidin assay is carried out in a solution of butanol-concentrated hydrochloric acid, where proanthocyanidins (condensed tannins) are converted to antho-cyanidins (products of autoxidation of carbocations formed by cleavage of interfla-vanoid bonds) (Matus-Cadiz and others 2008). 

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