Highlights Toujie Quwen Granules play an important role in the treatment of COVID-19. SARS-CoV-2 3CL hydrolase, RdRP, ACE2, IL-6 and S protein are the crucial enzymes for treating COVID-19. Molecular docking revealed the proposed binding characteristics between five enzymes and quercetin, calycosin, astragaloside IV, rutin, isoquercitrin. Contrary to rutin and astragaloside IV, quercetin and isoquercitrin bound to Spike protein rather than ACE2.

Cellulolytic enzymes from fungi are complex compound enzyme structures that generally include three kinds of hydrolytic enzymes, which are called endo-β-1,4-glucanases, exo-β-1,4-glucanases, and β-1,4-glucosidases (β-glucosidases). The fungus Mucor ardhlaengiktus isolated from field rice straw produced a β-glucosidase (MaBgl). Maximal MaBgl production occurred when M. ardhlaengiktus was incubated for 6 days in fermentation liquor at 30 °C and an initial pH of 6. Purified MaBgl was obtained from M. ardhlaengiktus fermentation broth by ammonium sulfate fractional precipitation and DEAE-Sepharose FF ion exchange chromatography. The molecular weight of MaBgl as determined by SDS-PAGE electrophoresis was approximately 72 kDa. The kinetic parameters, Michaelis constant (Km) and maximum velocity (Vmax), of MaBgl were 78.2 μmol/L and 28.5 μmol/(L·min), respectively. Assays of MaBgl produced by M. ardhlaengiktus RSC1 under different conditions were investigated by the 3,5-dinitrosalicylic acid (DNS) assay for glucose. The pH and temperature optima for catalytic activity of MaBgl were pH 4.8 and 50 °C, respectively. MaBgl exhibited good thermal stability in the range of 20 to 30 °C, but the thermal stability of MaBgl decreased rapidly over 60 °C. MaBgl had better pH stability between pH 4.6 and 5.0, and the stability of MaBgl decreased when the pH value was lower or higher than this range.