Anti-Inflammatory Effect of Essential Oils Extracted from Wood of Four Coniferous Tree Species

The aim of this study was to evaluate the anti-inflammatory effects of essential oils extracted from the wood of Chamaecyparis obtusa, Pinus densiflora, Pinus koraiensis, and Larix kaempferi. Essential oils were extracted by hydrodistillation, and their chemical components were determined by GC/MS. Major chemical components of these essential oils were α-cadinol (19.25%), τ-muurolol (14.20%), and α-pinene (13.74%) in C. obtusa; α-pinene (47.16%), longifolene (14.31%), β-phellandrene (11.78%), and β-pinene (11.02%) in P. densiflora; α-pinene (13.49%) and longifolene (10.79%) in P. koraiensis, and geranyl linalool (23.58%) and α-pinene (18.57%) in L. kaempferi. To evaluate the anti-inflammatory effects of essential oils, lipopolysaccharide (LPS)-induced RBL-2H3 mast cells were treated with these essential oils; then, the changes in the mRNA expression level of the cytokines IL-4 and IL-13 were examined. Further, degranulation was evaluated by measuring β-hexosaminidase release. After LPS-induced RBL-2H3 mast cells were exposed to 10−7% of all types of essential oils, the gene expression levels of IL-4 and IL-13 within the cells remarkably decreased. The relative mRNA expression level of IL-4 was 69.6% in P. densiflora, 63.2% in P. koraiensis, 55.1% in C. obtusa, and 45.8% in L. kaempferi compared with that in the group treated with LPS. The mRNA expression level of L-13 should a similar trend. The inhibitory rate of IL-13 mRNA expression of P. densiflora, P. koraiensis, C. obtusa, and L. kaempferi was 57.8%, 57.1%, 51.1%, and 34.5%, respectively. β-Hexosaminidase release significantly decreased following the treatment with the four types of essential oils. The rate of β-hexosaminidase release were 38.1% C. obtusa; 33.0% P. densiflora; 27.4% P. koraiensis; and 9.1% L. kaempferi. Among all types of essential oils, that extracted from P. densiflora wood showed the highest anti-inflammatory activity. These results show that the tested essential oils exert an anti-inflammatory effect through the inhibition of degranulation and expression of cytokines.