In nature, tannins abound in plant tissues, particularly in woody ones. We find them then in the barks, but also in the seeds, in the leaves and in the fruits, especially if unripe.
The unpleasant taste of an unripe fruit derives partly also from its high content of tannins. In fact, these molecules are synthesized by the plant to protect it from the attack of pests, insects and herbivores. The tannins also have an antioxidant function for the plant and often protect it by isolating it from atmospheric agents.
Tannins abound in many herbal drugs ; among those most used for the quantity of tannins contained in them we mention: witch hazel (leaves or bark of Hamamelis virginiana L.), bistta ( Polygonum bistorta L.), oak bark (from various species of Quercus ), walnut (leaves and husk of Junglans regia L), ratania (roots of Krameria trianda Ruitz et Pavon) and tormentilla (roots of Potentilla tormentilla )
In the picture some green and other dried witch hazel leaves coarsely chopped.
