Chymase inhibition: A key factor in the anti-inflammatory activity of ethanolic extracts and spilanthol isolated from Acmella oleracea.

ETHNOPHARMACOLOGICAL RELEVANCE

Acmella oleracea (L.) R. K. Jansen (Asteraceae), known as jambú in Brazil, is used in traditional medicine as analgesic and for inflammatory conditions, characterized by the presence of N-alkylamides, mainly spilanthol. This bioactive compound is responsible for the above-described pharmacological properties, including sialagogue and anesthetic.

AIM OF THE STUDY

This study aimed to characterize the anti-inflammatory effects of A. oleracea leaves (AOEE-L) and flowers (AOEE-F) extracts, including an isolated alkylamide (spilanthol), using in vitro and in vivo models. The mechanism underlying this effect was also investigated.

MATERIALS AND METHODS

Extracts were analyzed by HPLC-ESI-MS/MS in order to characterize the N-alkylamides content. AOEE-L, AOEE-F (25-100 μg/mL) and spilanthol (50-200 μM) were tested in vitro on VSMC after stimulation with hyperglycemic medium (25 mM glucose). Their effects over nitric oxide (NO) generation, chymase inhibition and expression, catalase (CAT), superoxide anion (SOD) radical activity were evaluated. After an acute administration of extracts (10-100 mg/mL) and spilanthol (6.2 mg/mL), the anti-inflammatory effects were evaluated by applying the formalin test in rats. Blood was collected to measure serum aminotransferases activities, NO activity, creatinine and urea.

RESULTS

A number of distinct N-alkylamides were detected and quantified in AOEE-L and AOEE-F. Spilanthol was identified in both extracts and selected for experimental tests. Hyperglycemic stimulation in VSMC promoted the expression of inflammatory parameters, including chymase, NO, CAT and SOD activity and chymase expression, all of them attenuated by the presence of the extracts and spilanthol. The administration of extracts or spilanthol significantly inhibited edema formation, NO production and cell tissue infiltration in the formalin test, without causing kidney and liver toxicity.

CONCLUSION

Taken together, these results provide evidence for the anti-inflammatory activity of leaves and flowers extracts of jambú associated distinctly with their chemical profile. The effects appear to be associated with the inhibition of chymase activity, suppression of the proinflammatory cytokine NO and antioxidant activities.