In silico antiviral properties of Spirulina platensis phycobiliprotein and phycobilin as natural inhibitor for SARS-CoV-2

The global pandemic COVID-19 in 2019 has led to a continued search for promising potential molecules to combat human viral diseases. An in silico strategy was attempted to narrow down the discovery of potentially active compounds for drug candidates. It has been reported that several bioactive molecules in cyanobacteria have displayed antiviral activities. This study aimed to investigate the potential of phycobiliprotein and phycobilin from Spirulina platensis, a nutrient-dense cyanobacterium, as anti-SARS-CoV-2 using in silico assessment. The docking of the drug candidate was performed by targeting three important SARS-CoV-2 protein receptors; main protease (M^pro₎, receptor binding domain (RBD), and RNA-dependent RNA polymerase (RdRp). The results revealed that phycoerythrobilin showed the high binding affinity against all target proteins, specially towards RBD and RdRp proteins that exceeded the chloroquine as well as remdesivir as control inhibitors. Inferiorly, phycocyanobilin showed also similar triple inhibitory effect against the three main proteins though lower affinity at SARS-CoV-2 M^pro when compared to inhibitor nelfinavir. Pharmacokinetics analysis was conducted for both compounds using SwissADME and pkCSM to provide the properties of bioactive candidates when designed as a drug. The molecular physicochemical evaluation showed that both phycocyanobilin and phycoerythrobilin have fulfilled the Lipinski's rule of five, suggesting that both molecules have drug-like properties and could act like a drug. Based on the simulation results, it can be concluded that phycobiliprotein and phycobilin from Spirulina platensis have the potential to be developed as source for the development of novel natural antiviral agent.