Anti-inflammatory and immunomodulatory effects of Critonia aromatisans leaves: Downregulation of pro-inflammatory cytokines

Abstract

Ethnopharmacological relevance: Critonia aromatisans (Asteraceae), commonly known as "Chiople", is a cultivated species that is used in Mayan traditional medicine to treat inflammation, joint pain and rheumatism.

Aim of the study: To evaluate the in vivo and in vitro anti-inflammatory and immunomodulatory properties of aqueous and organic extracts prepared from Critonia aromatisans leaves.

Materials and methods: Methanol, ethyl acetate, methylene chloride, hexanic, and aqueous extracts were obtained from the leaves of C. aromatisans. The anti-inflammatory properties of the extracts were tested in vivo to evaluate their ability to reduce the inflammatory response in the carrageenan-induced hind paw edema model in NIH mice. In addition, to explore the immunomodulatory effects of C. aromatisans, in vitro testing was performed to determine whether C. aromatisans leaf extracts are capable of decreasing macrophage production of nitric oxide (NO), tumour necrosis factor alpha (TNF-α), and cytokines IL-1β, IL-6, and cyclooxygenase 2 (COX-2) without affecting macrophage viability.

Results: Single orally administered doses (100mg/kg or 200mg/kg) of a hexanic extract of C. aromatisans leaves significantly reduced carrageenan-induced paw edema in mice (P<0.001) by 76% and 84%, respectively. The effect of the extract in this model was generally comparable to those of the standard drugs used. In the in vitro determination, the extracts reduced the amount of NO mainly at 500 and 1000μg/mL. Hexanic extract and subfractions C, D, E, and F at 50 and 100μg/mL produced the lowest concentration of mediators in culture supernatants (protein) and at the mRNA/gene level by the significant down-regulation of cytokines. These findings explain some of the anti-inflammatory activity of this species. Purification of fractions C and D allowed the complete identification of cyclocolorenone, stigmasterol and stigmasterol derivatives as some of their main components.

Conclusion: A hexanic extract of C. aromatisans displayed anti-inflammatory effects, validating the traditional practice of Mayan communities wherein an ointment with a petrolatum base, a non-polar substance, is used to treat inflammation. Additionally, C. aromatisans showed strong in vivo and in vitro activity, and one of the mechanisms of its anti-inflammatory response was shown to be inhibition of the production of NO and pro-inflammatory cytokines. The results of this study provide a pharmacological basis for the use of C. aromatisans leaves in the treatment of inflammatory disorders. The presence of stigmasterol and cyclocolorenone could be the responsibles of the anti-inflammatory activity of this specie. Further studies should be done on the antioxidant and anti-inflammatory properties of cyclocolorenone. The results of this study provide a pharmacological basis for the use of C. aromatisans leaves in the treatment of inflammatory disorders.

Keywords: Critonia aromatisans; Cyclocolorenone; Eupatorium hemipteropodum; Inflammation; Stigmasterol; Tnf-α.