Fig. 4.

Effect of QG on LPS-induced extracellular secretion of TNFalpha in RAW264.7 macrophage cells. RAW264.7 cells were pretreated with indicated concentrations of QG for 1 hr, then incubated with LPS (200 ng/ml) for 24 hrs. The concentration of TNFalpha in collected cell culture media was measured by ELISA assay as described in the methods. Although quercetin significantly suppressed LPS-induced TNFalpha cytokine in a concentration-dependent manner, QG showed a negligible effect in LPS-stimulated TNFalpha production. The values are expressed as mean ± SD for three independent experiments. ^**p<0.01 indicate statistically significant differences from treatments with LPS alone. QC and Q stand for quercetin-3-O-β-D-glucuronide and quercetin, respectively. Quercetin was used as a reference. Examination of quercetin at 100 μM concentration was not done due to the decreased cell viability.