Effects of prenylated flavonoids and biflavonoids on lipopolysaccharide-induced nitric oxide production from the mouse macrophage cell line RAW 264.7

Certain flavonoid derivatives possess anti-inflammatory activity in vitro a nd in vivo. Besides their antioxidative properties and effects on the arach idonic acid metabolism including cyclooxygenase/lipoxygenase inhibition, sa me flavones and flavonols were previously found to show inhibitory activity on nitric oxide production by inducible nitric oxide synthase (iNOS; NOS t ype 2) through suppression of iNOS induction. As part of our continuing inv estigations, the effects of unique and minor flavonoids (prenylated flavono ids and biflavonoids) on nitric oxide production from lipopolysaccharide-in duced macrophage cell line (RAW 264.7) were evaluated in order to establish their inhibitory activity on NO production and correlate this action with their in vivo anti-inflammatory potential. Among the derivatives tested, pr enylated compounds including morusin, kuwanon C, and sanggenon D and biflav onoids such as bilobetin and ginkgetin were found to inhibit NO production from lipopolysaccharide (LPS)-induced RAW 264.7 cells at >10 muM. Inhibitio n of nitric oxide production was mediated by suppression of iNOS enzyme ind uction but not by direct inhibition of iNOS enzyme activity. An exception w as echinoisoflavanone that inhibited iNOS enzyme activity (IC50 = 83 muM) a nd suppressed iNOS enzyme induction as well. While most prenylated derivati ves showed cytotoxicity to RAW cells at 10 - 100 muM, all biflavonoids test ed were not cytotoxic. Since nitric oxide (NO) produced by inducible NO syn thase (iNOS) plays an important role in inflammatory disorders, inhibition of NO production by these flavonoids may contribute, at least in part, to t heir antiinflammatory and immunoregulating potential in vivo.