Antiviral effects of phytochemicals against severe acute respiratory syndrome coronavirus 2 and their mechanisms of action: A review

The worldwide spreading of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has posed a serious threat to health, economic, environmental, and socialaspects of human lives. Currently, there are no approved treatments that can effec-tively block the virus although several existing antimalarial and antiviral agents havebeen repurposed and allowed use during the pandemic under the emergency useauthorization (EUA) status. This review gives an updated overview of the antiviraleffects of phytochemicals including alkaloids, flavonoids, and terpenoids against theCOVID-19 virus and their mechanisms of action. Search for natural lead moleculesagainst SARS-CoV-2 has been focusing on virtual screening and in vitro studies onphytochemicals that have shown great promise against other coronaviruses such asSARS-CoV. Until now, there is limited data on in vivo investigations to examine theantiviral activity of plants in SARS-CoV-2-infected animal models and the studieswere performed using crude extracts. Further experimental and preclinical investiga-tions on the in vivo effects of phytochemicals have to be performed to provide suffi-cient efficacy and safety data before clinical studies can be performed to developthem into COVID-19 drugs. Phytochemicals are potential sources of new chemicalleads for the development of safe and potent anti-SARS-CoV-2 agents