Anti-inflammatory activity of Cymbopogon citratus leaves infusion via proteasome and nuclear factor-κB pathway inhibition: Contribution of chlorogenic acid

Ethnopharmacological relevance: Cymbopogon citratus (DC.) Stapf leaves infusion is used in traditional medicine for the treatment of inflammatory conditions, however little is known about their bioactive compounds. Aim of the study: Investigate the compounds responsible for anti-inflammatory potential of Cymbopogon citratus (Cy) on cytokines production induced by lipopolysaccharide (LPS) in human and mouse macrophages, and the action mechanisms involved. Materials and methods: An essential oil-free infusion of Cy was prepared and polyphenol-rich fractions (PFs) were obtained from it by column chromatography. Chlorogenic acid (CGA) was identified, by HPLC/PDA/ESI-MSn. The expression of cytokines, namely TNF-alpha and CCL5, was analyzed by real-time RT-PCR, on LPS-stimulated human macrophages. Activation of nuclear factor (NF)-kappa B, a master regulator of inflammation, was investigated by western blot and gene reporter assay. Proteasome activity was assessed using a fluorogenic peptide. Results: Cymbopogon citratus extract and its polyphenols inhibited the cytokine production on human macrophages. This supports the anti-inflammatory activity of Cy polyphenols in physiologically relevant cells. Concerning the effect on the activation of NF-kappa B pathway, the results pointed to an inhibition of LPS-induced NF-kappa B activation by Cy and PFs. CGA was identified, by HPLC/PDA/ESI-MSn, as the main phenolic acid of the Cy infusion, and it demonstrated to be, at least in part, responsible by that effect. Additionally, it was verified for the first time that Cy and PFs inhibited the proteasome activity, a complex that controls NF-kappa B activation, having CGA a strong contribution. Conclusions: The results evidenced, for the first time, the anti-inflammatory properties of Cymbopogon citratus through proteasome inhibition and, consequently NF-kappa B pathway and cytokine expression. Additionally, Cy polyphenols, in particular chlorogenic acid, were highlighted as bioactive compounds. (C) 2013 Elsevier Ireland Ltd. All rights reserved.