key: cord-0800438-m36l5dxk authors: Pendyala, Brahmaiah; Patras, Ankit; Dash, Chandravanu title: Phycobilins as potent food bioactive broad-spectrum inhibitor compounds against Mpro and PLpro of SARS-CoV-2 and other coronaviruses: A preliminary Study date: 2020-11-24 journal: bioRxiv DOI: 10.1101/2020.11.21.392605 sha: 1f470667c0d7b97a3d753b92b0a4a6a9da5c16a8 doc_id: 800438 cord_uid: m36l5dxk In the twenty first century, we have witnessed three corona virus outbreaks; SARS in 2003, MERS in 2012 and ongoing pandemic COVID-19. To prevent outbreaks by novel mutant strains, we need broad-spectrum antiviral agents that are effective against wide array of coronaviruses. In this study, we scientifically investigated potent food bioactive broad-spectrum antiviral compounds by targeting Mpro and PLpro proteases of CoVs using in silico and in vitro approaches. The results revealed that phycocyanobilin (PCB) showed potential inhibitor activity against both proteases. PCB had best binding affinity to Mpro and PLpro with IC50 values of 71 μm and 62 μm, respectively. In addition, in silico studies of Mpro and PLpro enzymes of other human and animal CoVs indicated broad spectrum inhibitor activity of the PCB. Like PCB, other phycobilins such as phycourobilin (PUB), Phycoerythrobilin (PEB) and Phycoviolobilin (PVB) showed similar binding affinity to SARS-CoV-2 Mpro and PLpro 4 diseases in farm and domestic pet animals (Cavanagh, 2007; Pederson, 2009; Pratelli, 2006; 82 Odend 'hal, 1983) . 83 Till now, there are no approved vaccines and therapeutic drugs for COVID-19 or other 84 human coronavirus infections, and lack of enough clinical trial data to make treatment decisions. 85 Although vaccines have been developed against animal viruses IBV, canine CoV, and TGEV to 86 help prevent serious diseases (Liu & Kong, 2004; Carmichael, 1999; Park et al., 1998) , some 87 potential problems such as; recombination events between field and vaccine strains, emergence of CoV lifecycle. The M pro acts on minimum 11 cleavage sites of replicase 1ab, ~790 kDa; at 105 recognition sequence Leu-Gln↓(Ser, Ala, Gly) (↓ indicates cleavage site) for most cleavage 106 sites, block viral replication (Zhang et al., 2020). PL Pro enzyme hydrolyses the peptide bond at 107 carboxyl side of glycine (P1 position) and releases nsp1, nsp2, and nsp3 functional proteins, 108 which play key role in viral replication (Rut et al., 2020) . Therefore, these proteases would be 109 potential targets for development of broad-spectrum antiviral drugs. The crystal structures of 110 CoVs M pro and PL pro enzymes are available for public access in protein data bank (PDB) ( Table 111 2). Natural phytochemicals based drugs are gaining importance in the modern world healthcare 113 sector, because of its less toxicity, effective health benefits and its potential use in conjunction The crystal structures of M pro (PDB ID -6LU7) and PL pro of SARS-CoV-2 (PDB ID -6WUU) 125 and other CoVs (PDB ID numbers were given in Table 2 ) used in this study were obtained from 126 RCSB protein data bank. Ligand structures were obtained from Pubchem and Chemical Entities 127 of Biological Interest (ChEBI) as SDF format, Open Babel was used for format transformation or to delete other chains, heteroatoms (included water), adding missing atoms, hydrogens, charges. The files (pdbqt) were further prepared for proteins and ligands binding. and PL pro assays, and the mean value was presented with ± standard deviation (SD). Xanthophyllastaxanthin, carotenes -β-carotene, phenolic alkaloidcapsaicin, phenolic ketone 184 gingerol, phenolic aldehydevanillin, allylbenzeneeugenol, monoterpenoid phenolthymol. (Fig. 2) . Over all in silico docking and in vitro enzyme inhibitor 222 activity results showed PCB as a potent inhibitor against SARS-CoV-2 M pro and PL pro . In addition 223 to above mentioned studies (Table S1) The broad-spectrum efficacy of PCB against CoVs was evaluated by molecular docking 231 studies with available crystal protein data bank (PDB) structure of various human and animal 232 CoVs. Table 2 docking score (-9.3 K.cal/mol) for MERS M pro followed by HCoV NL63 (-9.0 K.cal/mol) and IBV 237 (-8.9 K.cal/mol). For PL pro , docking scores were in the range of -8.9 to -7.6 K.cal/mol. The results 238 revealed that PCB had higher binding affinity to dimer form of PL pro enzymes than monomeric 239 forms. When compared monomers only, PCB had best docking score for MERS-CoV (-8.5 240 K.cal/mol) followed by TGEV (-8.1 K.cal/mol) and SARS-CoV-2 (-8.0 K.cal/mol). Figure S2 Figure S5 . In conclusion, by using, in silico molecular docking, invitro enzymatic assay screenings, we 277 discovered PCB as potent phytochemical inhibitors to M pro and PL pro proteases of SARS-CoV-2. Clinical predictors of mortality of Middle East Respiratory Syndrome Coronavirus 290 (MERS-CoV) infection: A cohort study. Travel medicine and infectious disease Biosynthesis of phycobilins Combating emerging viral threats Severe respiratory illness caused by a novel coronavirus Canine viral vaccines at a turning point-a personal 299 perspective. 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