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

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