One of a diverse group of complex phenolic compounds commonly found in leaves, unripe fruits, and the bark of trees. Tea, chocolate, and wine are among the common tannin-rich foods. Tannins help defend the plant against pathogens and herbivorous animals by virtue of their astringent taste. They also reduce digestibility of the plant material by forming complexes with proteins, carbohydrates, and other nutrients, which causes satiety in the grazing animal. Some tannins have commercial uses, notably in the production of leather and ink.