Neutrophil Immunomodulatory Activity of Farnesene, a Component of Essential Oils.

Despite their reported therapeutic properties, not much is known about the immunomodulatory activity of essential oils present in species. We isolated essential oils from the flowers and leaves of five species: , , , , and . The chemical composition of the essential oil samples had similarities and differences as compared to those previously reported in the literature. The main components of essential oils obtained from , , , and were camphor (23.0-51.3%), 1,8-cineole (5.7-30.0%), camphene (1.6-7.7%), borneol (2.3-14.6%), artemisiole (1.2-7.5%), terpinen-4-ol (2.0-6.9%), α-pinene (0.8-3.9%), and santolinatriene (0.7-3.5%). Essential oils from were enriched in methyl chavicol (38.8-42.9%), methyl eugenol (26.1-26.4%), terpinolene (5.5-8.8%), (/)-β-ocimene (7.3-16.0%), β-phellandrene (1.3-2.2%), -cymen-8-ol (0.9-2.3%), and xanthoxylin (1.2-2.2%). A comparison across species also demonstrated that some compounds were present in only one species. Although essential oils were weak activators of human neutrophils, they were relatively more potent in inhibiting subsequent neutrophil Ca mobilization with -formyl peptide receptor 1 (FPR1) agonist MLF- and FPR2 agonist WKYMVM, with the most potent being essential oils from . Further analysis of unique compounds found in showed that farnesene, a compound with a similar hydrocarbon structure as lipoxin A, inhibited Ca influx induced in human neutrophils by MLF (IC = 1.2 μM), WKYMVM (IC = 1.4 μM), or interleukin 8 (IC = 2.6 μM). Pretreatment with essential oils and farnesene also inhibited human neutrophil chemotaxis induced by MLF, suggesting these treatments down-regulated human neutrophil responses to inflammatory chemoattractants. Thus, our studies have identified farnesene as a potential anti-inflammatory modulator of human neutrophils.