ABSTRACT
The novel coronavirus (SARS-CoV-2) has caused large-scale global outbreaks and mainly mediates host cell entry through the interaction of its spike (S) protein with the human angiotensin-converting enzyme-2 (ACE-2) receptor. As there is no effective treatment for SARS-CoV-2 to date, it is imperative to explore the efficacy of new compounds that possess potential antiviral activity. In this study, we assessed the potential binding interaction of the beneficial components of Chaga mushroom, a natural anti-inflammatory and immune booster with that of the SARS-CoV-2 receptor-binding domain (RBD) using molecular docking, MD simulation, and phylogenetic analysis. Beta glycan, betulinic acid, and galactomannan constituents of Chaga mushroom exhibited strong binding interaction (-7.4 to -8.6 kcal/mol) forming multivalent hydrogen and non-polar bonds with the viral S1-carboxy-terminal domain of the RBD. Specifically, the best interacting sites for beta glycan comprised ASN-440, SER 373, TRP-436, ASN-343, and ARG 509 with average binding energy of -8.4 kcal/mol. The best interacting sites of galactomannan included ASN-437, SER 373, TRP-436, ASN-343, and ALA 344 with a mean binding energy of -7.4 kcal/mol; and the best interacting sites of betulinic acid were ASN-437, SER 373, TRP-436, PHE 342, ARG 509, and ALA 344 that strongly interacted with the S-protein (ΔG = -8.1 kcal/mol). The docking results were also compared with an S-protein binding analog, NAG and depicted similar binding affinities compared with that of the ligands (-8.67 kcal/mol). In addition, phylogenetic analysis using global isolates depicted that the current SARS-CoV-2 isolates possessed a furin cleavage site (NSPRRA) in the RBD, which was absent in the previous isolates that indicated increased efficacy of the present virus for enhanced infection through increased interaction with ACE-2. The results showed that Chaga could be an effective natural antiviral that can supplement the current anti-SARS-CoV-2 drugs.
ABSTRACT
The most challenging threat facing the global community today is the coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Despite global efforts to develop suitable treatments, very few specific antiviral agents have been suggested and the virus remains a serious global health risk. In vivo animal experiments have demonstrated that bioactive mycochemical constituents of Inonotus obliquus have immunomodulatory, antimicrobial, and antiviral properties. The present study investigates the antiviral potential of I. obliquus terpenoids against COVID-19 using a molecular docking study. The in silico study elucidates the ability of most of the terpenoid components to interact with the receptor-binding domain of SARS-CoV-2 spike glycoprotein with excellent affinity. Additionally, we found that both betulinic acid and inonotusane C could bind and stably interact with the spike protein near the host cell recognition site of angiotensin-converting enzyme 2.