Down-regulatory effect of quercitrin gallate on nuclear factor-κB-dependent inducible nitric oxide synthase expression in lipopolysaccharide-stimulated macrophages RAW 264.7

Quercetin 3-O-β-(2″-galloyl)-rhamnopyranoside (QGR) is a naturally occurring quercitrin gallate, a polyphenolic compound isolated from Persicaria lapathifolia (Polygonaceae). In the present study, QGR compound was discovered to have inhibitory effect on nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated macrophages RAW 264.7. QGR compound attenuated LPS-induced synthesis of both mRNA and protein of inducible nitric oxide synthase (iNOS), in parallel, and inhibited LPS-induced luciferase expression as a reporter of iNOS promoter activity in the macrophages. As a mechanism of the anti-inflammatory action shown by QGR compound, suppression of nuclear factor (NF)-κB activation has been documented. QGR compound exhibited inhibitory effect on LPS-mediated NF-κB transcriptional activity in macrophages RAW 264.7. Furthermore, the compound inhibited LPS-mediated nuclear translocation of NF-κB p65 and DNA binding activity of NF-κB complex, in parallel, but did not influence LPS-mediated IκBα degradation. Taken together, QGR compound suppressed LPS-mediated NF-κB activation, specifically to nuclear localization step of NF-κB p65, which was attributable to its down-regulatory action on LPS-induced NO production and iNOS expression.