The emergence of the severe acute respiratory syndrome‐associated to COVID‐19 as pandemic; presents new challenges to global biomedical research. At current scenario, according to Johns Hopkins University & Medicine database, the virus has affected 181 countries. As on April 4, 2020, total confirmed cases suffering from COVID 19 were 1,131,713 and 59,884 people have died1. The appearance of COVID‐19 has also impacted transplantation worldwide2. In December of 2019, reports emerged of pneumonia clusters at Wuhan as they were linked to a wet animal wholesale market in the region. After a lot of epidemiologic investigation with International Committee on Taxonomy of Viruses; WHO officially announced identification of corona virus as COVID‐19 or SARS‐CoV‐23,4. Original diagnostic findings in family cluster cases at China included fever, dry cough, shortness of breath, rhinitis, fatigue, diarrhea, headache, symptoms of pneumonia and low lymphocyte count. Chest CT scans of the patients showed bilateral patchy shades in the lungs 5.
Coronaviruses are enveloped, (+) single stranded RNA viruses with a crown like appearance, belongs to the family Coronaviridae, order Nidovirales which is further divided into four genera (α, β, γ and δ),, subgenera Sarbecovirus, species is SARS‐CoV6. Four CoVs commonly found among humans: HCoV2–229E, -HKU1, -OC43 and -NL63. Novel CoV–2 is a zoonotic form of the beta-coronavirus which can rapidly mutate and recombine although mutations are natural part of the virus life cycle7,8.
COVID‐19 usually, has an incubation period of 2‐7 days and up to 14 days as longest time from infection to symptoms9. Throat swab, nasal swab, sputum, blood samples and stool are tested using viral nucleic acid with different techniques including real‐time reverse transcription polymerase chain reaction, whole‐genome sequencing, paper‐based bio-molecular sensors, nanopore target sequencing, antibody‐based immunoassays, and the clustered regularly interspaced short palindromic repeats‐Cas system10.
Drug development against coronavirus includes inhibition of viral replication through acting on its critical enzymes. As the viral genome (29891nucleotide) encodes more than 20 proteins, among which RNA-dependent RNA polymerase, helicase, spike, two proteases (PLpro and 3CLpro) are vital 11. A large segment of population with the highest mortality from CoV‐19 were elder people and individuals with weak immune system12,13. Therefore, interferons enhancement, monoclonal antibodies administration actively or passively can improve the immune response against the virus. Zinc is also reported to have antiviral effect by inhibiting CoV RNA polymerase activity and thus decreases viral growth in cell culture set up14,15. A receptor-binding domain (RBD) of the spike protein in SARS-CoV, mediates the interaction with host angiotensin-converting enzyme 2 (ACE–2)16. The drug, chloroquine affects the glycosylation process of ACE–2, which is essential for interaction with the host. It increases endosomal pH and thus makes unfavorable environment for the cell/virus fusion17.
The treatment with conventional drugs is intricate as multidrug resistance due to accumulating mutations in viruses however natural products provide broad spectrum antivirals agents with minimum side effects18. In Ayurveda, several medicinal plants namely; Tinospora cordifolia, Ocimum sanctum, Leucas cephalotes, Allium sativum, Allium cepa, Citrus limon, Piper nigrum, Phyllanthus emblica have been reported for antiviral activities19–21. They are endowed with a variety of secondary metabolites such as tannins, terpenoids, flavonoids, flavones, glycosides, alkaloids, phytosteroids and thus, herbal agents can be promising candidates for evaluating their effects on pathogenic microbes22. Therefore, the present study aims to analyze the docking potential of predominant phyto-constituents in the reported plants as inhibitors of 193CLpro in search of therapeutic potential against COVID 19 infection.