| Summary: | In a previous study, we demonstrated the anti-inflammatory activity of the essential oil extracted from Korean pine (<i>Pinus koraiensis</i>, Sieb. et Zucc.) wood. This study aims to investigate the active anti-inflammatory constituents of <i>P. koraiensis</i> oil. The essential oil was extracted from <i>P. koraiensis</i> wood by hydrodistillation and was divided into six fractions (A–F) through fractional distillation. Then, the anti-inflammatory activities of the fractions (A–F) were determined. Fractions A and F markedly downregulated the production of pro-inflammatory cytokines as well as the secretion of <i>β</i>-hexosaminidase in lipopolysaccharide (LPS)-stimulated RBL-2H3 cells. The main constituents of the active anti-inflammatory A and F fractions were (+)-<i>α</i>-pinene, (−)-<i>β</i>-pinene, (+)-<i>α</i>-terpineol, 3-carene, (+)-limonene, and longifolene. These six single compounds decreased the expression of inflammatory-related genes (i.e., IL-4 and IL-13) as well as the secretion of <i>β</i>-hexosaminidase in LPS-stimulated RBL-2H3 cells. (+)-<i>α</i>-Pinene, (−)-<i>β</i>-pinene, (+)-<i>α</i>-terpineol, and longifolene exhibited the strongest effects; these effects were comparable to those of the positive control (i.e., dexamethasone). The findings indicate that the interactions between these components exhibit potential for the management and/or treatment of inflammatory conditions as well as base structures for the development of novel anti-inflammatory drugs.
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