2.8 Data analysis
The MS RAW files were converted to mgf format by MSconvert and output by
pLabel v2.4.1. GraphPad Prism 7.0 was used to calculate the
IC50 and KI values.
Results
3.1
Screening
the antiviral herbs with strong anti-SARS-CoV-2 Mproeffect
First of all, the anti-SARS-CoV-2 Mpro potentials of
60 antiviral herbs were assessed, while the residual activity of
the protease was measured by a FRET-based assay. As shown inFig.2 , LJ exhibited potent inhibitory effects on
Mpro at a final concentration of 100 μg/mL, resulting
in a residual activity of 6.55%. Subsequent assays revealed that LJ
could block the activity of SARS-CoV-2 Mpro in a time-
and dose- dependent manner. The IC50 value for
preincubation of 63 minutes was determined as 37.82±1.038 μg/mL(Fig. 2). Moreover, we used
DTT sensitivity analysis to verify
the inactivation mechanism of Mpro by Lonicera
japonica . In the absence of DTT, the residual activity of 100 ug/mL LJ
on Mpro was close to 0. In contrast, the addition of 1
mM DTT resulted in almost no inhibition of Mpro(Fig. S2) . These results suggested that LJ could potently and
time-dependently inhibit Mpro mainly through the
interactions with cysteines of this viral enzyme.