Antiviral compounds lignans

Besides antitumor/anticancer activity, lignans are among the most potent antiviral compounds, although most of the lignans evaluated for antiviral potency belong to families of plants other than Taxaceae [3]. 

Lignans are a well-known class of widespread natural phenolic compounds that exhibit great structural and biological diversity and are commonly found in vascular plants from various families [1]. They are present at different levels of abundance in all plant parts, including roots, rhizomes, hardwood, bark, stems, leaves, flowers, fruits and seeds [2]. Lignans are of considerable pharmacological and clinical interest and are used in the treatment of cancer and other diseases [3]. The extensive pharmaceutical use of lignans is due to their antitumor, antiviral and hepatoprotective properties as well as many other beneficial activities. 

In order to explain and confirm the biological activities claimed by the traditional medicine, and to search for new biologically active compounds we studied the antimicrobial, antioxidative, immunomodulatory, antiinflammatory, skin-regenerating and antiviral properties of Fraxinus ornus bark extract and its components. In a parallel detailed phytochemical investigation of the extract we isolated and determined the structures of many hydroxycoumarins, secoiridoid glucosides, caffeoyl esters of phenylethanoid glycosides, lignans and other phenolic compounds. 

At least 40 lignans are known to have antitumor and antiviral activity and many are cytotoxic (Ayres and Loike, 1990 Davin et al., 1992 MacRae and Towers, 1984 Mac-Rae et al., 1989), although there are no common structural features to explain this activity. Podophyllotoxin (51) (Fig. 8.15), which has been isolated from a number of plant species, is a potent antineoplastic (i.e., tumor destructive) compound. Although too toxic for practical value, synthetically... 

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