Tannins (tannins) are compounds naturally produced by plants. They belong to polyphenols and are highly reactive compounds. Tannins are water-soluble and have a molecular weight in the range of about 500 to 3000 Da. Products with a high content of these compounds have a harsh, unpleasant taste and may be toxic.
In the case of plants, Tannins have a defensive function, deterring herbivores. Among other things, tannins are present in the bark of oak, willow, spruce, chestnut, larch, walnut leaves, sage, wine, tea, nuts, in many fruits (such as blueberries, strawberries, raspberries, cranberries, grapes, pomegranates, apples), in St. John’s wort, cinquefoil, turnip rape, cistus infusion and legume seeds, buckwheat, dark chocolate and cocoa.
Tannins – breakdown
We divide tannins into two types:
- hydrolysing – in the center of the molecule is a monosaccharide, the hydroxyl groups of which are esterified with gallic acid residues or its derivatives; are easily hydrolysed to weak acids and bases or enzymes;
- non-hydrolysing (condensed) – they do not contain saccharide in the molecule, they are found in unripe fruits and seeds, which under the influence of ripening are broken down into compounds with smaller molecules.
Tannins – properties
Tannins are characterized by many properties that are beneficial to the human body, including:
- soothe irritations,
- reduce itching and burning,
- have anti-inflammatory and antibacterial properties,
- support the work of the immune system,
- prevent allergies.
Taken orally, they have an astringent effect on the mucous membranes, inhibit their permeability, preventing, for example, microbleeding from capillary blood vessels (primarily in the gastrointestinal tract).
According to scientists, tannins can protect against all kinds tumorsand also slow down the rate at which cancer cells divide. They can help to modify the microflora of the mouth and intestines, eliminating pathogenic organisms. Strong antioxidant properties of tannins neutralize free radicals that damage basic cell structures. They inhibit lipid peroxidation and multiplication of HIV. They also have an anti-carcinogenic effect. Easily hydrolysing tannins are broken down in the digestive tract. Tannins are also used to counteract the effects of alkaloids poisoning.
Tannins are also used to treat animal skin. The antioxidant activity of tannins is also important in extending the shelf life of food. An example is red wine, which, thanks to tannins, can mature for many years and is not oxidized. Due to the ease of combining tannins with metal ions, they are used to obtain dyes.
The overuse of plants rich in tannins hinders the absorption of, among others, vitamins, macro- and microelements in the gastrointestinal tract. Non-hydrolysing tannins decompose in the gastrointestinal tract into toxic compounds, causing poisoning, therefore eating unripe fruit should be avoided.