Identification, Characterization and Anti-inflammatory Activity of a New Flavonoid From Hibiscus mutabilis L.

<i>Hibiscus mutabilis</i> L (Malvaceae) was a traditional Chinese medicine with significant anti-inflammatory activity. We isolated 3 compounds from the flowers of <i>H mutabilis</i> L , including a new flavonoid, (1″R)-8-(1-(3,4-dihydroxyphenyl)ethyl)-3,3',5,7-tetrahydroxy-4'-methoxyl flavone (<b>1</b>), and 2 known flavonoids (<b>2-3</b>). The structures of these compounds were elucidated by various spectroscopic methods. In addition, we evaluated the anti-inflammatory effect of compound <b>1</b>. The bioactivity assay showed that <b>1</b> significantly inhibit the excessive production of IL-6, TNF-α and NO in LPS-induced RAW264.7 macrophages. Western blot analysis demonstrated that <b>1</b> inhibit the expressions of COX-2 and iNOS protein in the macrophages induced by LPS in a concentration-dependent manner. In addition, <b>1</b> also significantly suppress the expression of the key proteins P65 and p-P65 in the NF-<i>κ</i>B signaling pathway. Our results revealed that <b>1</b> exert potential anti-inflammatory activity through inhibiting the activation of NF-<i>κ</i>B signaling pathway.