Phellinus linteus mycelia extract in COVID-19 prevention and identification of its key metabolic compounds profiling using UPLC-QTOF-MS/MS spectrometry.

For centuries, food, herbal medicines, and natural products have been valuable resources for discovering novel antiviral drugs, uncovering new structure-activity relationships, and developing effective strategies to prevent/treat viral infections. One such resource is Phellinus linteus, a mushroom used in folk medicine in Taiwan, Japan, Korea, and China. In this rich historical context, the key metabolites of Phellinus linteus mycelia ethanolic extract (GKPL) impacting the entry of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) at multiple stages have yet to be explored. Thus, this study systematically identifies and assesses the inhibitory effect of GKPL on the SARS-CoV-2 virus. Initially, the concentrations and contact times of GKPL against SARS-CoV-2 pseudovirus were assessed in HepG2 cells. Subsequently, utilizing the Ultra Performance Liquid Chromatography-Quadrupole Time-of-Flight Mass Spectrometry method, potential biomarkers in the fungal extract were discerned. Metabolomic analysis identified 18 compounds in GKPL, with hispidin and hypholomine B present in the highest amounts. These compounds were isolated using chromatographic techniques and further identified through 1D NMR spectroscopic and mass spectrometry analysis. Hispidin and hypholomine B were found to inhibit the infection of SARS-CoV-2 pseudovirus by reducing angiotensin-converting enzyme 2 gene expression in HepG2, thereby decreasing viral entry. Moreover, hispidin and hypholomine B effectively block the spike receptor-binding domain, while hypholomine B, for the first time, showed significant inhibition of 3CL protease. This suggests that GKPL, enriched with hispidin and hypholomine B, has the potential to be used as an active ingredient against SARS-CoV-2.