Phytochemicals as Antiviral Agents: Recent Updates

The epidemic of viral diseases is a global concern, mandating an urgent need of most promising antivirals. Some of the viral diseases can be cured by approved antiviral drugs, but for others still do not have any vaccines or drugs available. Most of the approved antiviral drugs are somehow directly or indirectly associated with side effects, which eventually raise the need for the development of antivirals based on natural phytochemicals. Globally, the development of antivirals is shifting towards the plant-derived products as they are less toxic and has less chance to develop resistance. Phytochemicals have been exploited traditionally for the cure of many diseases, and also have been reported to inhibit viral replication/transcription. Most of them inhibit the viruses either during the viral entry inside the host cell or during their replication. Moreover, 50% of the drugs derived from plants are being used in the Western nations. Plants have a variety of phytochemicals like flavonoids, terpenoids, lignins, alkaloids, and coumarins that are having antioxidant activity, and help to inhibit viral genome. Various plant-derived products have been well studied against viruses like herpes virus, human immunodeficiency virus (HIV), influenza, and hepatitis virus. More recently, Coronavirus disease (COVID-19) caused by a newly identified coronavirus has become pandemic, and affected world’s population severely. However, there are still less explored phytochemicals for the inhibition of viruses like dengue virus, chikungunya virus, and other alphaviruses. In this chapter, we will emphasize on the reported phytochemicals and their derivatives, having antiviral properties and their mechanism to treat viral diseases.