Imperialine and Verticinone from Bulbs of Fritillaria wabuensis Inhibit Pro-inflammatory Mediators in LPS-stimulated RAW 264.7 Macrophages.

The bulbs of plants belonging to the Fritillaria cirrhosa-group have been used as antitussive and expectorant herbs in traditional Chinese medicine for thousands of years. In this study, we isolated two isomers of verticinone and imperialine, steroidal alkaloids belonging to the cevanine group, from bulbs of Fritillaria wabuensis, which is a part of the Fritillaria cirrhosa group, and investigated their anti-inflammatory effects and relative mechanisms on lipopolysaccharide-stimulated RAW 264.7 macrophages. Our results clearly demonstrate that verticinone or imperialine could dose-dependently inhibit nitric oxide production and also suppress inducible nitric oxide synthase and cyclooxygenase-2 expressions. In addition, verticinone or imperialine suppress the production of pro-inflammatory cytokines in a dose dependent manner, such as tumor necrosis factor-α and interleukin-1β. The effect of verticinone and imperialine on the activation of nuclear factor-kappaB was also evaluated. The phosphorylation of nuclear factor-kappaB stimulated with LPS is also down-regulated by verticinone or imperialine in a concentration dependent manner, which coincided with the inhibition of phosphorylation forms of inhibitory kappaB-α, a crucial inhibitory factor of nuclear factor-kappaB. Generally, the anti-inflammatory effects and mechanisms of verticinone and imperialine are mediated by the inhibition of the nuclear factor-kappaB activation signaling pathway. According to the results of our researches, verticinone and imperialine may present great potentials to be developed as therapeutics for inflammatory diseases.