Antiviral activity of Conyza canadensis (L.) Cronquist extracts grown in Tunisia

Herbal medicine represents one of the most important fields of traditional medicine all over the world. There has been growing interest in the investigation of natural products from plants for the discovery of new antimicrobial agents. The appearance of viral resistant strains to antiviral agents is an emerging problem. Thus, the prevalence of viral related diseases is of great concern. For this reason, the development of new and better antiviral compounds is vital and desirable. It has been demonstrated that natural products are preferable to synthetic compounds as sources of new antiviral agents (Vanden et al., 1986; Vlietinck and Vanden, 1991; Abad et al., 1997). A number of compounds with inhibitory activity against the replication of several viruses have been extracted from a number of medicinal plants (De Rodriguez et al., 1990, 1996; Marchetti et al., 1996; Hayashi et al., 1997). Conyza canadensis (L.) Cronquist belongs to the family of Compositae and is native to North America (Weaver, 2001). This plant also grows spontaneously in central Tunisia. Whole plant has been used as a Tunisian folk medicine for the treatment of rheumatism. It also has antidiarrhoeal and antihaemorrhoidal activities (Chevallier, 1996; Chiej, 1984;