**1.4.1 Antiviral substances**

Presented antiviral activity of fungi is related to their whole, complex extracts, but also to the isolated compounds. Agents isolated from fungi can directly cause the inhibition of viral enzymes, the synthesis of viral nucleic acid, or adsorption and absorption of virus in mammalian cells. The most often small molecules are active in the direct antiviral effect, while the indirect effects are mediated by antiviral activity immunostimulative polysaccharides and other complex molecules (Zjawioni, 2004).
