A Method for Isolating Condensed Tannins from Crude Plant Extracts with Trivalent Ytterbium uri icon

abstract

  • A method to precipitate condensed tannin from crude plant extracts using trivalent ytterbium has been developed. The new method requires less time and resources than the condensed isolation procedure using Sephadex LH-20 recommended by Hagerman (1991, Tannin Analysis, Miami University, Oxford, OH, USA). The absorbance of the preparations obtained by precipitation with trivalent ytterbium was similar to the preparations obtained with the original isolation procedure, when the acid butanol method (Porter et al 1986, Phytochemistry 1 223-230) was used to measure condensed tannins. Condensed tannins were isolated from crude plant extracts of three plant species, Desmodium ovalifolium, Gliricidia sepium and Manihot esculenta, and the condensed tannin content of the lyophilised leaf tissue was determined. For each plant species, the amounts of the soluble, insoluble and fibre-bound condensed tannins were estimated using five different standards. These standards included two tannin preparations obtained either by (1) isolation with Sephadex LH-20, or (2) by the precipitation with trivalent;ytterbium and three external standards: (3) cyanidin, (4) delphinidin and (5) purified quebracho (Schinopsis balansae). When external standards were used (cyanidin, delphinidin, purified quebracho), it was likely that the condensed tannin content of the plant tissue would be under- or overestimated. When an internal standard based on the isolated tannin from the respective plant species was used,accurate estimates were obtained.

publication date

  • 1997
  • 1997