Characterization of Condensed Tannins Purified From Legume Forages: Chromophore Production, Protein Precipitation, and Inhibitory Effects on Cellulose Digestion

Abstract

To identify simple screening tools for selecting condensed tannin (CT)-containing forages as candidate sources for further study, CT were isolated from nine legumes, and their molecular weights (MW), chromophore production, capacity to precipitate bovine serum albumin (BSA) and Fraction 1 protein (Rubisco) isolated from alfalfa, and inhibition of filter paper digestion were compared. Sources were as follows: leaves of sericea lespedeza (Lespedeza cuneata Dum.-Cours.), crown vetch (Coronilla varia L.), and sainfoin (Onobrychis viciifolia Scop.); stems of hedysarum (Hedysarum alpinum L.); seeds of alfalfa (Medicago sativa L.); and whole plants of birdsfoot trefoil (Lotus corniculatus var. corniculatus L.) and three varieties of big trefoil (Lotus pedunculatus Cav.), viz., Lotus uliginosus Schkuhr, L. uliginosus var. glabriusculus, and L. uliginosus var. villosus. Molecular weights and sizes (degrees of polymerization) of the CT varied considerably within and among plant species. Average MW ranged from 3036 Da (crown vetch) to 7143 Da (lespedeza). All CT exhibited greater capacity (w/w basis) to bind alfalfa Rubisco than BSA. Relative astringencies (microg CT required to precipitate 1 mg protein) against BSA ranged from 262.5 for CT from lespedeza to 435.5 for CT from L. corniculatus, and against Rubisco, from 49.6 (sainfoin) to 108.2 (alfalfa seed). Including CT at 300 microg/ml in cultures of Fibrobacter succinogenes reduced digestion of cellulose filter paper by 19.8% (sainfoin) to 92.4% (crown vetch) and increased the specific activity of cell-associated endoglucanase. There were no correlations between inhibitory effects of CT on filter paper digestion and (1) chromophore formation during CT assay by butanol-HCl, vanillin-HCl, or H2SO4; (2) precipitation of BSA or alfalfa Rubisco; and (3) MW of CT. The most inhibitory CT for cellulose digestion included those with broad and with narrow MW distributions. Sainfoin was the most desirable source of CT, as it had the highest capacity to bind alfalfa protein and was least inhibitory to cellulose digestion by F. succinogenes. This study suggests that these properties are not easily defined via chemical means, and that biological assays using rumen bacteria may help identify those CT with properties of nutritional interest.

Chemical characterization and in vitro biological activity of four tropical legumes, Styzolobium aterrimum L., Styzolobium deeringianum, Leucaena leucocephala, and Mimosa caesalpiniaefolia, as compared with a tropical grass, Cynodon spp. for the use in ruminant diets

“…Condensed tannins are phenolic compounds classified as polymers of flavan 3-ol with different molecular weights that can bind protein and other macromolecules (Mueller-Harvey, 2006). The binding is reversible according to pH and molecular type (McAllister et al, 2005) and is sometimes considered beneficial as it can reduce nematode damages, bloat, and ruminal protein degradation (Mueller-Harvey, 2006). Some of the negative ef-fects are low palatability, digestibility reduction, and reduced performance (Makkar, 2003a).…”

Nutrient composition and degradation profiles of anthocyanidin-accumulating Lc-alfalfa populations

“…Mots clé s: Luzerne, anthocyanidine, transge`ne Lc, sous-fractions prote´inique et glucidique, ratio de de´gradation azote-hydrates de carbone Alfalfa (Medicago sativa L.), also known as lucerne, is one of the most important forages in the world (Smith et al 2000;Wang et al 2006b) because of high yield and high nutrient levels (McMahon et al 2000;Popp et al 2000;Yu et al 2003). A major disadvantage of grazing cattle on alfalfa is its poor protein utilization (Broderick 1995;Yu et al 2004) and its tendency to cause pasture bloat Wang et al 2006b).…”

“…Pasture bloat arises from rumen fermentation gases, which become trapped in a stable protein foam that prevents normal eructation of gas via the oesophagus by the animal (Cockrem et al 1987;Tanner et al 1995). Characteristic bloat-free legume forages like sainfoin (Onobrychis viciifolia), sulla (Hedysarium coronarium), birdsfoot trefoil (Lotus corniculatus), and big trefoil (Lotus pedunculatus) contain condensed tannin (CT), flavonoid polymers, which are also known as proanthocyanidin (Aerts et al 1999;Majak et al 1995;McMahon et al 2000). Condensed tannins complex with protein in the rumen and reduce ruminal protein degradation, which can increase the efficiency of protein utilization (Aerts et al 1999;Broderick 1995) and reduce in vitro foam stability (Fay et al 1980;Tanner et al 1995).…”

In Vitro Evaluation of Anthelmintic Efficacy of Some Plant Species Possessing Proteinases and/or Other Nitrogenous Compounds in Small Ruminants

“…Goats browse and graze, whereas untrained sheep graze, rendering tree parts such as shoots, leaves, growing parts of shrubs and forbes main constituents of goats' diet [40]. These forages contain plenty of plant secondary metabolites, some of which are implicated in control of parasitic nematodes and other microbial organisms [41,42]. Sheep on their part seldom encounter these plant secondary metabolites because their diet is predominantly grass in nature [39].…”