Fig. 1.

Quercetin inhibits SARS-CoV-2 infection. Vero E6 (A) or Caco2 (B) cells were pre-treated with various concentrations of quercetin (ranging from 6.25 µM to 400 µM) before being infected with SARS-CoV-2 at an MOI of 0.1. Supernatants were harvested after 48 h, and virus RNA was quantified via RT-qPCR. RNA levels are expressed on an inverse y-axis as Ct (cycle threshold) values. Results were obtained from three independent experiments and are expressed as mean Ct values ± SD (C and D). Cell viability after 48 h incubation with quercetin in the same concentration range was determined for Vero E6 (E) and Caco2 (F) cells using the CyQUANT™ XTT Cell Viability Assay kit