Antivirals of ethnomedicinal origin: structure-activity relationship and scope.

Ethnomedicinal plants have been used as source of candidate drugs for almost all diseases, but the number of compounds having antiviral activity is scarce. Irrespective of type of viruses and the cells they infect, there are a very few specific viral targets for the natural molecules to interact. Most of the available antiviral drugs often lead to the development of viral resistance coupled with the problem of side effects, recurrence and viral latency. A wide array of ethnomedicinal plants showed high level of antiviral activities and many of them have complementary and overlapping mechanism of action, either inhibiting viral replication, or viral genome synthesis. Hence, there is an urgent need to develop new antivirals of natural origin. This review will cover some of the promising antiviral compounds isolated from ethnomedicinal plants with proven in vitro and some documented in vivo activities, along with their structure activity relationship.