The Coronavirus Disease 2019 (COVID-19) is a pandemic caused by the outbreak of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and has resulted in increasing mortality and socio-economic burden. It is associated with high fever, cough, severe shortness of breathing, nausea, vomiting, and diarrhea in human populations; and has caused + 10 M infections with more than 0.5 M deaths worldwide.
1,2 The pathogen, which is a new member of the betacoronavirus genus, is a positive-sense and single-stranded RNA virus similar to SARS-CoV and MERS-CoV (the Middle East Respiratory Syndrome coronavirus).
3 Along with structural proteins (like spike glycoprotein and accessory proteins), these viral genomes encode non-structural proteins, including 3-chymotrypsin-like protease, papain-like protease, helicase and RNA-dependent RNA polymerase (RdRp).
4At present, no preventive vaccines or established antiviral therapies are available against COVID-19.
5However, several repurposed drugs such as remdesivir, hydroxychloroquine, and chloroquine phosphate have shown promising results.
6,7 Virtual screening, which is associated with search space minimization, economic feasibility, and high versatility, may be particularly valuable for rapidly finding a potent inhibitor of the COVID-19 virus. In the search for anti-coronavirus agents, important druggable targets include 3-chymotrypsin-like protease (3CLpro), papain-like protease (PLpro), RNA-dependent RNA polymerase (RdRp), and spike (S) proteins.
8 The RdRp, a multi-domain protein, is a central component of coronaviral replication/transcription machinery that is able to catalyze RNA-template dependent formation of phosphodiester bonds between ribonucleotides in the presence of divalent metal ion.
9–11 The polymerase domain is highly conserved and shares common structural features among coronaviruses, Hepatitis C Virus and other positive sense RNA viruses.
12–14 Thus, the viral RdRp or its catalyzed polymerization process has been explored as targets for developing several anti-viral drugs for treating Hepatitis C, Zika and coronaviruses.
13,15–17Exploiting the potentials of phytomedicine, which is perhaps the oldest, and most assorted of all therapeutic systems, is an integral component of the international response to the COVID-19 pandemic, as highlighted by the WHO-China Joint Mission on COVID-19. Phytomedicine has efficacy against COVID-19 as many antiviral plants native to China have shown promising therapeutic potential against SARS-CoV and SARS-CoV-2
16,18,19 African herbs and medicinal plants provide a vibrant resource for chemopreventive phytochemicals as they could accumulate secondary metabolites more than plants from the northern hemisphere.
20,21African plants and phytochemicals with documented antiviral, antimicrobial, antimalarial, antifungal exploited towards the development of prophylactic and therapeutic agents against the COVID-19.
22–25 This study focused on virtual screening of phytochemicals derived from African herbs and medicinal plants against the COVID-19 and related virus RNA-dependent RNA polymerase.
