New synthetic anti-inflammatory chrysin analog, 5,7-dihydroxy-8-(pyridine-4yl)flavone.

To identify anti-inflammatory flavonoid derivatives with optimal chemical structures, various 8-heterocyclic-substituted chrysin derivatives were previously synthesized and their effects on prostaglandin E₂ (PGE₂) production from the lipopolysaccharide (LPS)-treated mouse macrophage cell line, RAW 264.7, were evaluated. Through this screening procedure, 5,7-dihydroxy-8-(pyridine-4yl)flavone (C-721) among the derivatives was selected for further pharmacological study. Contrary to the parent molecule, chrysin, C-721 was found to potently inhibit PGE₂ and NO production by LPS-treated RAW cells. The IC₅₀ values of C-721 were 6.2 and 22.6μM, respectively, for cyclooxygenase-2 (COX-2) mediated PGE₂ and inducible nitric oxide (iNOS)-mediated NO production. Western blotting and reverse transcriptase-polymerase chain reaction analysis demonstrated that this compound inhibited PGE₂ production, at least in part, via COX-2 down-regulation and COX-2 inhibition, while C-721 primarily inhibited NO via down-regulation of iNOS expression. In addition, C-721 inhibited TNF-α and IL-6 production at 10-50 μM. An in vivo study revealed that oral and intraperitoneal administration of C-721 showed 25.2%-44.3% inhibition against λ-carrageenan-induced paw edema in mice at 10-100mg/kg. Furthermore, this compound significantly inhibited collagen-induced arthritis in mice when administered by intraperitoneal injection at 50mg/kg three times/week. Taken together, these results suggest that C-721 has the potential for use as a synthetic lead compound for development of a new anti-inflammatory agent.