Natural products and phytochemicals as potential anti-SARS-CoV-2 drugs

The current pandemic responsible for the crippling of the health care system is caused by the novel SARS-CoV-2 in 2019 and leading to coronavirus disease 2019 (COVID-19). The virus enters into humans by attachment of its Spike protein (S) to the ACE receptor present on the lung epithelial cell surface followed by cleavage of S protein by the cellular transmembrane serine protease (TMPRSS2). After entry, the SARS-CoV-2 RNA genome is released into the cytosol, where it highjacks host replication machinery for viral replication, assemblage, as well as the release of new viral particles. The major drug targets that have been identified for SARS-CoV-2 through host-virus interaction studies include 3CLpro, PLpro, RNA-dependent RNA polymerase, and S proteins. Several reports of natural compounds along with synthetic products have displayed promising results and some of them are Tripterygium wilfordii, Pudilan Xiaoyan Oral Liquid, Saponin derivates, Artemisia annua, Glycyrrhiza glabra L., Jinhua Qinggan granules, Xuebijing, and Propolis. This review attempts to disclose the natural products identified as anti-SARS-CoV-2 based on in silico prediction and the effect of a variety of phytochemicals either alone and/or in combination with conventional treatments along with their possible molecular mechanisms involved for both prevention and treatment of the SARS-CoV-2 disease.