Antiviral activity of plants and their isolated bioactive compounds: An update

Viral infections represent one of the main causes of disease worldwide, especially today due to the increase of migration, global travel, and urbanization. The several side effects of the conventional drugs and the growing phenomenon of resistance have led researchers to turn to the plant kingdom as a source of potential new antiviral drugs. The aim of this work is to summarize the updated evidence for antiviral activity of different plants and their isolated bioactive compounds, evaluating also the potential interactions, which can occur in cotreatment with conventional antiviral drugs. The plant complexes have proved to be usually more active than their most abundant isolated compounds by hypothesizing synergistic mechanisms. In addition to cellular and molecular investigations, molecular docking studies have proved essential in highlighting the interaction mechanisms of bioactive compounds with target molecules. However, the use of nonstandardized extracts, or too high concentrations in vitro, which do not reproduce their bioavailability in vivo, are often limiting factors. Moreover, the lack of studies concerning the safety profile of plant extracts and their isolated compounds, alone or in combination with conventional antiviral drugs, is the most worrying aspect. In light of this, further studies are needed to validate their possible therapeutic use.