Quercitrin blocks the effector SipA translocation of T3SS. (A) Chemical structure of quercitrin. (B) Growth curve of S. Typhimurium SL1344 with quercitrin treatment for 6 h. (C) Quercitrin inhibits the effector SipA translocation to eukaryotic host cells of S. Typhimurium T3SS (Magnification 200×). The untreated group was set as 100%. WT (pSipA-TEM), positive control group. △invA-SL1344, negative control group. WT (pSipA-TEM) + 16 μL/mL Quercitrin, quercitrin treatment group. Blue fluorescence represents normal effector translocation, and green fluorescence represents blocked translocation. (D) Quantitative data of quercitrin inhibiting the effector SipA translocation were collected for statistical analysis by blue/green ratio (=response ratio) from five different visual fields. Blue/green ratio = blue cells/green cells. The response ratio meeting the baseline requirements should be at least less than 1.0, ** p < 0.01, compared with the WT (pSipA-TEM) group.