Fig. 1

Identification of bis-benzylisoquinoline alkaloids as SARS-CoV-2 entry inhibitors. a Schematic diagram of the screening workflow with selection criteria for hits outlined. b Scatter plot of primary screening of 188 compounds against S-G614 infection. Inhibition ratios for all drugs obtained in a preliminary screening are represented by scattered points. Red dots indicate the 41 compounds with an inhibition rate ≥70%. DMSO (green dot) and aloxistatin (blue dot) were used as a negative and positive control, respectively. c–g Dose-response curves of five selected compounds (c) SC9, (d) SC161, (e) SC171, (f) SC182, (g) SC185 on VSV-G, S-D614, S-G614, S-SARS, S-MERS, N501Y.V1, and N501Y.V2 pseudoviruses. h Chemical structures of SC9, SC161, SC171, SC182, and SC185. i Inhibitory effect of SC9, SC161, SC171, SC182, and SC185 at 5 μM on SARS-CoV-2 S mediated cell-cell fusion. j Effect of extracellular and intracellular Ca²⁺ depletion on S-G614 pseudovirus entry in 293T-ACE2 cells. k–l Inhibition curves (k) and EC₅₀ values (l) of the compounds against S-G614 pseudovirus entry in the presence of 20 μM BAPTA-AM. m The inhibitory effect of the compounds on native SARS-CoV-2 infection by observing their cytopathogenic effects. SC9, SC161, SC171, and SC185 were tested at 10 μM, and DMSO and remdesivir (5 μM) were used as a negative and positive control, respectively. n The relative viral RNA levels in the SC9, SC161, SC171, and SC185 (10 μM) treatment groups were 0.08%, 70.27%, 43.55%, and 76.98% respectively. *P < 0.05; **P < 0.01; ***P < 0.001. All experiments were repeated at least three times