Figure 4.

Effect of quercetin on hemagglutination and hemolytic activity. (a) Overnight cultures of P. gingivalis with quercetin were harvested, and suspended in PBS. 100 μL of PBS was added to each well in a 96-well round-bottom microtiter plate, 100 μL of the bacterial cells was suspended in PBS, added to the first well and serially diluted (1:2 to 1:128). Sheep erythrocytes suspension (100 μL, 2% in PBS) and quercetin were added to each well, and the plate was incubated for 3 h. Hemagglutination activities were evaluated visually. (b) P. gingivalis cells were centrifuged, re-suspended to a final OD_600nm of 1.5. The sheep erythrocytes at a concentration of 1% were mixed with an equal volume of bacterial cells with or without quercetin at 37 °C for 18 h. The hemolytic activity was determined at wavelength of 405 nm. Bars denoted by (****) indicate significant difference at p < 0.0001 by one-way analysis of variance (ANOVA) with Dunnett's post hoc test.