Antcin-B for COVID-19

Abstract Antcins obtained from the fruiting bodies of Taiwanofungus camphoratus, have been traditionally used to treat infections, whereas their role in the SARS-CoV-2 3-chymotrypsin-like protease (3CLPro) remains unclear. We employed both in vitro and in silico approaches to understand the underlying chemical mechanism comprehensively. Our finding revealed that various antcins (A, B, C, H, I, and M) and non-antcins (citronellol and limonene) exhibited lower toxicity to cells than GC376, along with favorable drug-likeness based MTT assay and ADMET prediction. Molecular docking analysis predicted that antcin-B possessed the lowest binding affinity energy and interacts with key residues such as Glu169, Gln189, His41, Leu141, Asn142, Glu16, and His165 employing hydrophobic interaction, hydrogen bonding, and salt bridge. These interactions were further confirmed by molecular dynamics (MD) simulation, which demonstrated the formation of hydrogen bonds with Asn142 and Gly143 and bridge with Glu166 for approximately 40% and 70% of the simulation time, respectively. Indeed, in vitro, 3CLPro activity analysis supports the above notion that antcin-B significantly (96.39%) inhibits 3CLPro activity, which is highly comparable with a known antiviral drug GC367 (96.72%). Consequently, antcin-B could be considered for developing a potential drug candidate for inhibiting 3CLPro activity, thereby impeding reducing the severity of COVID-19 in patients.

AbstractDespite the remarkable development of highly effective vaccines, including mRNA-based vaccines, within a limited timeframe, coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is not been entirely eradicated. Thus, it is crucial to identify new effective anti-3CLPro compounds, pivotal for the replication of SARS-CoV-2. Here, we identified an antcin-B phytosterol-like compound from Taiwanofungus camphoratus that targets 3CLPro activity. MTT assay and ADMET prediction are employed for assessing potential cytotoxicity. Computational molecular modeling was used to screen various antcins and non-antcins for binding affinity and interaction type with 3CLPro. Further, these compounds were subjected to study their inhibitory effects on 3CLPro activity in vitro. Our results indicate that antcin-B has the best binding affinity by contacting residues like Leu141, Asn142, Glu166, and His163 via hydrogen bond and salt bridge and significantly inhibits 3CLPro activity, surpassing the positive control compound (GC376). The 100 ns molecular dynamics simulation studies showed that antcin-B formed consistent, long-lasting water bridges with Glu166 for their inhibitory activity. In summary, antcin-B could be useful to develop therapeutically viable drugs to inhibit SARS-CoV-2 replication alone or in combination with medications specific to other SARS-CoV-2 viral targets.