Aloin isoforms (A and B) selectively inhibits proteolytic and deubiquitinating activity of papain like protease (PLpro) of SARS-CoV-2 in vitro.

Devin S M Lewis, Joanna Ho, Savannah Wills, Anasha Kawall, Avini Sharma, Krishna Chavada, Maximilian C C J C Ebert, Stefania Evoli, Ajay Singh, Srujana Rayalam, Vicky Mody, Shashidharamurthy Taval

Research output: Contribution to journalArticlepeer-review


The most common host entry point of human adapted coronaviruses (CoV) including SARS-CoV-2 is through the initial colonization in the nostril and mouth region which is responsible for spread of the infection. Most recent studies suggest that the commercially available oral and nasal rinse products are effective in inhibiting the viral replication. However, the anti-viral mechanism of the active ingredients present in the oral rinses have not been studied. In the present study, we have assessed in vitro enzymatic inhibitory activity of active ingredients in the oral mouth rinse products: aloin A and B, chlorhexidine, eucalyptol, hexetidine, menthol, triclosan, methyl salicylate, sodium fluoride and povidone, against two important proteases of SARS-CoV-2 PLpro and 3CLpro. Our results indicate only aloin A and B effectively inhibited proteolytic activity of PLpro with an IC 50 of 13.16 and 16.08 μM. Interestingly, neither of the aloin isoforms inhibited 3CLpro enzymatic activity. Computational structural modelling of aloin A and B interaction with PLpro revealed that, both aloin isoforms form hydrogen bond with Tyr 268 of PLpro, which is critical for their proteolytic activity. Furthermore, 100 ns molecular dynamics (MD) simulation studies predicted that both aloin isoforms have strong interaction with Glu 167 , which is required for PLpro deubiquitination activity. Our results from the in vitro deubiquitinase inhibition assay show that aloin A and B isomers exhibit deubiquitination inhibitory activity with an IC 50 value of 15.68 and 17.51 µM, respectively. In conclusion, the isoforms of aloin inhibit both proteolytic and the deubiquitinating activity of SARS-CoV-2 PLpro, suggesting potential in inhibiting the replication of SARS-CoV-2 virus.

Original languageAmerican English
JournalScientific Reports
StatePublished - Feb 9 2022


  • Animals
  • Binding Sites
  • COVID-19
  • Cell Survival
  • Chlorocebus aethiops
  • Coronavirus 3C Proteases
  • Coronavirus Papain-Like Proteases
  • Emodin
  • Humans
  • Molecular Dynamics Simulation
  • Protein Isoforms
  • SARS-CoV-2
  • Vero Cells


  • Medicine and Health Sciences

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