In this in silico study, it was investigated whether phycobilins
(phycocyanobilin, phycoerythrobilin, and phycourobilin) could be inhibitors
of the activity of the main proteins of the SARS-CoV-2 virus. All
chromophores exhibited a binding energy value of ? ?37 kJ mol?1 for
PLpro-WT, PLpro-C111S, helicase-ANP binding site, Nsp3-macrodomain,
Nsp3-MES site, and Nsp10/14-N7-Mtase. Phycocyanobilin showed the highest
binding energy of ?44.77 kJ mol?1 against the target protein PLpro-C111S. It
was found that, apart from the hydrogen bonds and hydrophobic interactions,
phycobilins also form electrostatic interactions with the SARS-CoV-2
proteins. The network of non-covalent interactions was found to be important
for the stability of the examined virus proteins. All phycobilins have good
pharmacokinetic and drug-likeness properties. This study's results suggest
that the screened phycobilins could serve as promising drugs for the
treatment of COVID-19 with further rigorous validation studies.