Mechanistic Aspects of Medicinal Plants and Secondary Metabolites against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2)

Background and Objective: Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), a highly pathogenic virus, is responsible for a respiratory disease termed coronavirus disease 2019 (COVID-19). SARS-CoV-2 genome encodes various structural and non-structural proteins, which are necessary for viral en -try and replication. Among these proteins, papain-like protease (PLpro), 3C-like protease (3CLpro), RNA-dependent RNA polymerase (RdRp), helicase, serine protease, and spike protein are potential targets of herbal remedies and phytocompounds for inhibition of viral infection and replication. There is, at present, no con-firmed cure for the COVID-19. Various plants and their components have been introduced against SARS-CoV-2. A number of review articles have also been published on them. This article is focused on the mechanistic as-pects of these plants and their derivatives on SARS-CoV-2. Methods: The material in this review article was prepared from significant scientific databases, including Web of Science, PubMed, Science Direct, Scopus and Google Scholar. Results: Different medicinal plants and their phytocompounds interact with important structural and non-structural of SARS-CoV-2 proteins. Natural compounds form strong bonds with the active site of SARS-CoV-2 protease and make large conformational changes. These phytochemicals are potential inhibitors of structural and non-structural SARS-CoV-2 proteins such as Spike protein, PLpro, and 3CLpro. Some important anti-SARS-CoV-2 actions of medicinal plants and their metabolites are: inhibition of the virus replication or entry, blocking the angiotensin-converting enzyme 2 (ACE-2) receptor and Transmembrane protease, serine 2 (TMPRSS2), regulation of inflammatory mediators, inhibition of endothelial activation, toll-like receptors (TLRs) and activation of the nuclear factor erythroid-derived 2-related factor 2 (Nrf2). Some of these important natural immune boosters that are helpful for the prevention and cure of various symptoms related to COVID-19 include Allium sativum, Nigella sativa, Glycyrrhiza glabra Zingiber officinalis, Ocimum sanctum, Withania somnifera, Tinospora cordifolia, and Scutellaria baicalensis. Also, Kaempferol, Quercetin, Baicalin, Scutellar-in, Glycyrrhizin, Curcumin, Apigenin, Ursolic acid, and Chloroquine are the best candidates for treating the symptoms associated with SARS-CoV-2 infection. Conclusion: Medicinal plants and/or their bioactive compounds with inhibitory effects against SARS-CoV-2 sup-port the human immune system and help in fighting against COVID-19 and rejuvenating the immune system.

Automated summary

This study reviewed the mechanism of action of plants and plant compounds against SARS-CoV-2, and their inhibitory effects on important viral proteins, including Spike protein, PLpro, and 3CLpro. Some medicinal plants and their metabolites with anti-SARS-CoV-2 actions intervene in virus replication and entry through various pathways, potentially valuable for preventing and treating symptoms related to COVID-19.