Comparison of the Precipitation of Alfalfa Leaf Protein and Bovine Serum Albumin by Tannins in the Radial Diffusion Method
✍ Scribed by Giner-Chavez, B I; Van Soest, P J; Robertson, J B; Lascano, C; Pell, A N
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 269 KB
- Volume
- 74
- Category
- Article
- ISSN
- 0022-5142
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✦ Synopsis
The precipitation of protein by condensed and hydrolysable tannins was evaluated with the radial di †usion method of Hagerman (1987) using bovine serum albumin (BSA) and isolated leaf protein from fresh alfalfa (Medicago sativa). Alfalfa leaf protein (AALP) was included at two concentrations, 25 and 156 mg N litre~1, at pH 6É8 and 39¡C to simulate rumen conditions. The condensed tannins were puriÐed from lyophilised samples of Arachis pintoi, Desmodium ovalifolium, Gliricidia sepium, Manihot esculenta and quebracho (Schinopsis balansae). Hydrolysable tannins from tannic acid (TA) were used as well. There was a signiÐcant interaction (P \ 0É001) between tannin and protein source, and protein level on protein precipitation. Most puriÐed condensed tannins (CTs) precipitated more AALP than BSA when protein was included at the same level. PuriÐed CT from quebracho and hydrolysable tannin from TA failed to precipitate AALP at both protein levels. In a second experiment, tannins from crude plant extracts were studied in the radial di †usion method using BSA and two levels of AALP. The crude plant extracts were obtained from lyophilised plant samples of A pintoi, Centrosema macrocarpum, Clitoria ternatea, D ovalifolium, Erythrina berteroana, E poepigiana, G sepium, M esculenta, Pueraria montana and P phaseoloides. The protein precipitated by soluble tannins in the plant samples was correlated to the total phenolic content and to the soluble CT estimated by the acid butanol assay or by the radial di †usion method. Tannins from di †erent plant species precipitated di †erent amounts of BSA and AALP. Therefore, the measures of the biological activity of tannins based on BSA precipitation may not reÑect the ability of tannins to precipitate proteins of plant origin such as those commonly found in the diets of herbivores. The present study o †ers the possibility of using the radial di †usion method with plant proteins at precipitation conditions similar to those in the rumen.