Novel bisabolane derivative from “arnica-da-serra” (Vernonieae: Asteraceae) reduces pro-nociceptive cytokines levels in LPS-stimulated rat macrophages

Abstract

Ethnopharmacology relevance Hydro alcoholic leaves extracts (HALE) of Lychnophora ericoides Mart. (“false arnica” or “arnica-da-serra”) had been popularly used against pain and inflammatory process. Aim The present work aimed to look for possible active volatile compounds that could be found in HALE of Lychnophora ericoides among the non volatile anti-inflammatory and analgesic compounds previously reported. Methods Harvests were performed during the end of the wet summer season (April) when scented branches were instantly collected and frozen. HALE's were simulated at the lab by following the procedures lectured by the locals. Mass Spectrometry experiments suggested structural information when using both EI–MS and ESI–MS/MS. After isolation through classical thin layer chromatography (TLC) procedures, the NMR experiments and signals assignments were carried out. The effects on the cytokines or nitric oxide (NO) production were assessed at in vitro assays that had monitored the levels of these substances on the supernatant of LPS-stimulated macrophage primary cell culture. Results The major metabolite from HALE was isolated from the essential oil and the major compound had its molecular formulae established by Mass Spectrometry (High Resolution) and its structure by NMR. Literature-based investigation enables us to define the structure of the new metabolite as 6-methyl-2-(4-methylcyclohex-4-enyl-2-acetyloxy) hept-5-en-2-ol and its name as orto-acetoxy-bisabolol. In vitro assay of interleukins release inhibition was carried out using rat peritoneal macrophages cultures. IL-1β and TNF-α levels were significantly reduced when cells were previously treated with low doses of orto-acetoxy-bisabolol, but neither IL-6 nor NO levels have their levels reduced. Results suggest that ethnical knowledge of anti-inflammatory and analgesic effects of the “arnica-da-serra” HALE may be associated to the orto-acetoxy-bisabolol ability on synthesis inhibition of the key inflammatory/hypernociceptive mediators. Conclusions Phytochemical investigation of the volatile active compounds in Lychnophora ericoides HALE allows us to isolate a new bisabolane derivative (orto-acetoxy-bisabolol) and to infer that this compound inhibits the synthesis of TNF-α and IL-1β, two important inflammatory mediators in the hypernociception. Our present data, in addition to literature's data, furnish scientific support to folk's use of Lychnophora ericoides as an endemic wound healer.