Bioactive Compounds from Medicinal Plants and their Possible Effect as Therapeutic Agents against COVID-19: A Review

Background: Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) has infected more than 117 million people worldwide and caused almost 2.6 million deaths. Currently, the appropriate therapeutic drugs are not yet available to treat diseases caused by this coronavirus infection. This is due to the fact that discoveries and developments of new medications require a lot of time and resources. The alternative solution for this viral infection is to utilize medicinal plant-based bioactive compounds as therapeutic agents to fight against COVID-19. Methods: Herein, through an extensive search of the literature, we reviewed the potential of some bioactive compounds from medicinal plants as therapeutic agents against COVID-19. The results of this review still require further investigation to clinically validate them, either in vitro or in vivo, in order to find the effective antiviral drugs from medicinal plants for COVID-19 treatment. Results: From a total of 60 identified medicinal plants, 50 of them have possible effects as therapeutic agents against particular target proteins encoded by the coronavirus genes such as Nsp1, Nsp3 (Nsp3b, Nsp3c, PL^pro and Nsp3e), Nsp7-Nsp8, Nsp9-Nsp10, Nsp14-Nsp16 complexes, 3CL^pro, E protein, ORF7a, Spike (S) glycoprotein, C-terminal RNA binding domain (CRBD), N-terminal RNA binding domain (NRBD), helicase and RdRp. The most common bioactive compounds from the medicinal plants as therapeutic agents for COVID-19 treatment were flavonoid compounds. Conclusion: Medicinal plants can serve as starting points for therapeutic agent development against some target proteins of SARS-CoV-2. Nevertheless, the results require clinical validation, either in vitro or in vivo, for COVID-19 treatment.