Tannin

Tannin is a chemical found in the leaves of many species of plant. Tea is one example of a plant with a naturally high tannin content, though in the case of green tea the leaf does not release its tannin into the infusion. In addition, new species of tea have been specifically bred for a lower tannin content. Tannin is also found in red wine which has been matured in oak or wood casks with a high tannin content.

Tannin is an important ingredient in the process of tanning leather.