Kuromoji (Lindera umbellata) essential oil (KEO) has long been used in Japan as a traditional medicine. It contains linalool (C 10 H 18 O), a naturally occurring small terpenoid. For this study, we investigated the antiinflammatory effect of KEO in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. Mouse macrophage-like RAW 264.7 cells were stimulated with LPS. Then they were treated with 25 or 50 g/mL of KEO for 24 h. KEO suppressed LPS-induced pro-inflammatory cytokine production such as that of nitric oxide (NO), interleukin-6 (IL-6), and tumor necrosis factor-(TNF-) in a dose-dependent manner. In addition, inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) mRNA expression and protein levels were suppressed by treatment with KEO cells. In addition, by treatment with 25 or 50 g/mL of linalool showed the same anti-inflammatory effect. The results suggest that KEO and linalool can be regarded as a natural resource for use in anti-inflammatory therapeutic products.

Abstract. Essential oils diluted from certain plants have been shown to have antitumor activity against several human tumor cell lines. Kuromoji (Lindera umbellata) essential oil (KEO) has long been used in Japan as a traditional medicine. KEO and its major chemical constituent, linalool, were investigated in this study for their ability to induce apoptosis and differentiation in human leukemia HL-60 cells. HL-60 cells were treated with 5 or 50 µg/ml KEO or linalool for 24 or 48 h. Then, cell proliferation and apoptosis induction were estimated. In addition, HL-60 cells are known to differentiate into granulocyte or monocytes by a variety of compounds. Therefore, the effect of KEO or linalool on differentiation of HL-60 cells was assessed by Giemsa stain and a nitroblue tetrazolium reduction assay. Cells treated with KEO or linalool for 48 h showed significantly suppressed cell proliferation, with induced apoptosis. Moreover, KEO and linalool promoted cell differentiation. Treatment with KEO cells at the same dose as linalool showed an almost identical effect on HL-60 cells. These results suggest that KEO and linalool have efficacy as anticancer therapeutic products.