Identification of Chromomoric Acid C-I as an Nrf2 Activator in Chromolaena odorata

Activation of nuclear factor-erythroid 2-related factor 2 (Nrf2) contributes to several beneficial bioactivities of natural products, including induction of an increased cellular stress resistance and prevention or resolution of inflammation. In this study, the potential of a crude leaf extract of Chromolaena odorata, traditionally used against inflammation and skin lesions, was examined for Nrf2 activation. Guided by an Nrf2-dependent luciferase reporter gene assay, the phytoprostane chromomoric acid C-I (1) was identified as a potent Nrf2 activator from C. odorata with a CD (concentration doubling the response of vehicle-treated cells) of 5.2 mu M. When tested at 1-10 mu M, 1 was able to induce the endogenous Nrf2 target gene heme oxygenase 1 (HO-1) in fibroblasts. Between 2 and 5 mu M, compound 1 induced HO-1 in vascular smooth muscle cells (VSMC) and inhibited their proliferation in a HO-1-dependent manner, without eliciting signs of cytotoxicity.