Essential Oil from Leaves of Liquidambar formosana Ameliorates Inflammatory Response in Lipopolysaccharide-activated Mouse Macrophages

Abstract

The essential oil from Liquidambar formosana leaves (EOLF) was demonstrated to exhibit anti-inflammatory activity in mouse macrophages. EOLF reduced nitrite oxide generation, secretion levels of tumor necrosis factor-α and interleukin-6, and expression levels of prointerleukin-1β, inducible nitric oxide synthase, and cyclooxygenase-2 in lipopolysaccharide (LPS)-activated mouse macrophages. EOLF also reduced NLRP3 inflammasome-derived interleukin-1β secretion. The underlying mechanisms for the EOLF-mediated anti-inflammatory activity were (1) reduction of LPS-induced reactive oxygen species generation; (2) reduction of LPS-induced activation of c-Jun N-terminal kinase, extracellular signal-regulated kinase, and p38 MAP kinase; (3) reduction of LPS-induced nuclear factor-κB activation. Furthermore, 25 compounds were identified in the EOLF using GC-FID and GC-MS and the major compounds were terpinen-4-ol (32.0%), β-pinene (18.0%), γ-terpinene (13.8%), and α-terpinene (9.7%). We found that LPS-induced nitrite oxide generation was inhibited significantly by terpinen-4-ol. Our results indicated that EOLF has anti-inflammatory activity and may provide a molecular rationale for future therapeutic interventions in immune modulation.