Occurrence

Tannins are widespread in the vegetable kingdom. They cause plants that contain them to assume reddish-brown colours; they are considered to be residues of plant metabolism. Some plants accumulate high quantities of tannins: seasoned wood from the quebracho tree, found in South America, contains more than 20% in weight of tannins, which are mainly used for the treating of animal skin. Generally speaking tannins are common in both Gymnosperms and Angiosperms. Within Angiosperms, they are more common in Dicotyledons than in Monocotyledons. Examples of families of Dicotyledons rich in tannins are:

- Leguminosae (e.g. wattle)

- Anacardiaceae (e.g. quebracho)

- Rhizophoraceae (e.g. mangrove)

- Myrtaceae (e.g. myrtle)

Other important sources of tannins include oak, willow and eucalyptus.

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