**Abstract**

*Tannins - Structural Properties, Biological Properties and Current Knowledge*

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**40**

Tannins possess a variety of biological effects, not a small part of which is of medical significance. Tannins, isolated from plants as well as synthetically obtained, manifest activity against a large spectrum of viruses: enteroviruses (polio- and coxsackie-), caliciviruses (feline calicivirus, mouse norovirus), rotavirus, influenza virus A, rhabdo- (vesicular stomatitis virus), paramyxoviruses (Sendai and Newcastle disease viruses), human immunodeficiency virus, herpes simplex virus, and adenoviruses. A special importance merits several ellagitannins manifesting pronounced effects against herpes simplex virus type 1 and 2 and on some herpes viruses affecting domestic animals, causing diseases of economic importance. An advantage of ellagitannins as anti-herpesvirus agents is that they have a non-nucleoside structure. Their targets are virus-specific proteins, so they retain activity against acyclovir-resistant strains of HSV types 1 and 2. Besides, these tannins manifest a synergistic effect with acyclovir when combined. Some initial results on their mechanism of action were carried out. In addition, it was found that most of the tannins have antioxidant properties in experimental models in vitro as well as in experimental influenza viral infection in mice.

**Keywords:** tannins, antiviral effect, antioxidant, herpes simplex virus, influenza virus
