Tannin Research Paper

Tannins

Tannins are polyphenolic compounds that are broadly categorized into two major groups:

1. Condensed tannins, or proanthocyanidins, consisting of oligomers of two or more flavan-3-ols, such as catechin, epicatechin, or the corresponding gallocatechin.

2. Hydrolysable tannins, consisting of a central core of carbohydrate to which phenolic carboxylic acids are bound by ester linkage.

Tannins have a very high affinity for proteins and form protein-tannin complexes. The ingestion of a plant containing condensed tannins decreases nutrient utilization, protein being affected to a great extent, and decreases feed intake. On the other hand, hydrolysable tannins are potentially toxic to animals. Consumption of feeds containing high levels

The great variety of species over which these compounds are found has grown as detection techniques have improved. Tannins are high molecular weight, water-soluble polyphenols that form reversible complexes with proteins through pH-dependent hydrogen bonding and hydrophobic interactions. Hydrolysable tannins (HT) contain a carbohydrate core esterified with gallic or hexa-hydroxyl-diphenic acids. Binding of HT to abomasal mucosal proteins causes lesions that result in diarrhea or constipation. Hydrolytic products of HT are absorbed from the small intestine; disrupt liver and kidney function, and cause photosensitization and dehydration. Condensed tannins (CT) or proanthocyanidins are oligomers of flavan-3-ols or flavan-3,4-diols that are linked by C-4/C-8 or C-4/C-6 inter flavan

Sometimes they act as toxins, rather than as inhibitors of digestion. The diversity of effects of tannins on digestion is partly due to the physiological capacity of animals to use and partly due to differences in the chemical reactions of different types of tannins. In some mammals, salivary proteins react with the tannins. In white tailed deer this tannin-binding salivary proteins are glycoproteins containing large amounts of proline, glycine and glutamate/glutamine.

Tannins are an important part of the characteristics that determine the palatability of plants by herbivores due to the astringent properties of these compounds. By this mean plant reduces herbivory frequency by ruminants and improve their chances of survival. It has been found that plants that receive more herbivore attack are able to increase their concentration of tannins. In general, tannins are more abundant in the parts of the plant that are more likely to be eaten by herbivores. Numerous reports illustrate the effects of environmental and seasonal factors as well as of phonological development. Very briefly, high temperatures, water stress, extreme light intensities and poor soil quality increase the tannin content of