The genomic structure of coronavirus is non-segmented positive strand RNA (+ssRNA) with nucleocapsid. It has single stranded genomes. It has four main structural proteins as spike glycoprotein, envelop glycoprotein, membrane glycoprotein and nucleocapsid protein. Several other accessory proteins are also present. Spike glycoprotein facilitates binding to host cells by attraction of angiotensin-converting enzyme 2 (ACE2) in lower respiratory tract in synergy with TMPRSS2 (transmembrane serine protease 2). The furin cleavage site of virus is essential for breakdown of Spike glycoprotein and it determines the entry of virus in host cells.
The nucleocapsid protein is localized in endoplasmic reticulum. It is bound to nucleic acid material of the virus. It is responsible for viral genome and replication cycle. It is also connected to response of host cells for viral infection. Membrane protein plays important role in determining the shape of the virus envelope while envelope protein helps in the production and maturation of virus.
Number of herbal compounds shown specific activities against different virus is being used to control covid-19 too. Recent studies reveal cucurmin with potentials to treat Covid-19 as it has got protease inhibitory effects with downregulation capacity for ACE receptor. Epigallocatechin gallate, kaemferol-7-glucoside, baicalin, scutellarin, hesperetin, glycyrrhizin, nicotianamine etc. are other compounds that target ACE2 receptors.
Epigallocatechin gallate is present with number of plants as leaves of Camellia sinensis, fruits of Terminalia bellirica, T. chebula etc. Smilax chinensis, Cassia renigera, Andrographis paniculata etc. contain kaemferol-7-glucoside. Baicalin and scutellarin are present many plants from Lamiaceae and Myrtaceae family. Citrus species are rich in hesperetin while Glcyrrhiza glabra contain glycyrhhizin. Herbal compounds are needed to be tested with potentials to inhibit the spike protein breakdown or ACE-2 receptor inhibition. Compounds targeting nucleocapsid protein may help in stopping signalling pattern.