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Health properties of tannins: what do they depend on?

Tannins are vegetable substances with astringent, anti-inflammatory, anti-diarrheal, antibacterial and haemostatic properties.

All these properties derive from the ability of tannins to bind tenaciously to the proteins present in the epithelial cells with which they come into contact, causing them to precipitate and coagulate. If we take for example the cells of the intestinal mucosa, the binding with tannins reduces the permeability and the secretive capacity of the mucosa; the villi, consequently, are waterproofed, even against irritating substances and micro-organisms.

It is therefore no coincidence that tannins are useful in case of diarrhea:

  • reduce mucous secretion
  • they hinder the passage of pathogens by reduction of intestinal permeability
  • neutralize phlogistic proteins
  • they dull the sensory nerve endings

Tannin-rich drugs are also used for local therapy of dermatitis and inflammation of the skin and mucous membranes, for the treatment of hemorrhoids and to promote the healing of small hemorrhagic wounds.

In the image to the side: chemical structure of tannic acid, the form in which tannin is marketed. The image helps us to understand how tannins are polyphenolic molecules; in fact they contain a large number of phenolic groups.