Insight into the Potential Antiviral Properties of the Genus Clerodendrum: Bioactive compounds with Mechanism of Action

Background: Antiviral compounds from plant origin have been the focus of researchers throughout the world for a long time as the potential alternative to classical antiviral therapies. The search for antiviral phytochemicals comes into the limelight amidst the recent COVID- 19 pandemic. This tremendous surge in the hunt for effective and alternative treatment from the plant source is mainly due to the toxicity and inadequate responses of synthetic antiviral drugs to resistant viral strains. Methods: A comprehensive literature survey on the antiviral activity of bioactive compounds from the genus Clerodendrum was conducted using known and widely acknowledged scientific databases. Results: This in-depth review is prepared to shed light on the promising effect of the bioactive phytochemicals isolated from different Clerodendrum spp. against some of the most pathogenically relevant viruses such as Severe Acute Respiratory Syndrome-Corona Virus-2 (SARS-CoV- 2), Human Immunodeficiency Virus (HIV), Influenza Virus, Hepatitis C Virus (HCV), Herpes Simplex Virus (HSV), Japanese Encephalitis Virus (JEV), Dengue Virus (DENV), and Chikungunya Virus (CHIKV). Bioactive compounds such as ursolic acid, sugiol, and quercetin are reported to prevent virus-host cell adhesion. Harpagide is found to reduce intracellular Ca2+ and mitochondrial stress in infected cells, preventing viral infection. Researchers reported the efficacy of β-sitosterol in inhibiting immune responses via RIG-I signalling and IFN production. Rengyolone is found to mitigate viral infection by preventing acute inflammation. Betulinic acid, tricin, and oleanolic acid are found to prevent IAV and HIV replication. Evidence has also suggested the possible action of kaempferol, acacetin and apigenin to inhibit mRNA and protein production in virus-infected cells. Conclusion: Future research should be oriented towards the isolation and quantitation of these bioactive compounds from Clerodendrum spp., along with their efficacy both in vitro and in vivo prior to their clinical applications in combating a variety of viral infections.