樟屬植物葉子精油之抗發炎活性

Abstract

過度的發炎反應（Inflammation）會破壞細胞及組織，亦與許多慢性疾病的病程發展有關，樟屬（Cinnamomum Trew.）植物富含特殊芳香成分及生物活性，其抗發炎之功效非常值得深入探究，因此，本研究藉由LPS誘導巨噬細胞RAW 264.7產生一氧化氮（Nitric oxide, NO）之發炎模式，評估肉桂醛型土肉桂（Cinnamomum osmophloeum ct. cinnamaldehyde, CO-Cin）、山肉桂（Cinnamomum insularimontanum, CI）、胡氏肉桂（Cinnamomum macrostemon, CM）、香桂（Cinnamomum subavenium, CS）、錫蘭肉桂（Cinnamomum zeylanicum, CZ）、陰香（Cinnamomum burmanii, CB）及枷羅木醇型土肉桂（C. osmophloeum ct. linalool, CO-LL）葉子精油的抗發炎活性；同時，為了解7種樟屬植物葉子精油之抗發炎機制，以西方墨點法（Western blot）分析葉子精油對iNOS與COX-2發炎蛋白表現的影響，同時亦探討其是否會影響HO-1抗氧化蛋白表現。 本研究結果得知，肉桂醛型土肉桂、胡氏肉桂、山肉桂及香桂葉子精油可顯著降低iNOS蛋白表現，進而抑制NO生成，其抑制NO生成之IC50值分別為13.1、35.1、40.2及41.8 μg/mL，具有良好的抗發炎活性；其中，胡氏肉桂葉子精油之抗發炎活性源自於主成分－E-Citral及Z-Citral兩異構物，其抑制NO生成之IC50值分別為15.9及19.9 μg/mL，兩者皆能降低iNOS蛋白表現及促進HO-1蛋白表現，具抗發炎及抗氧化活性，其中，E-Citral能調控NF-κB之Translocation，使NF-κB無法進入細胞核內，進而抑制iNOS表現；此外，Z-Citral及E-Citral於精油內之混合比值為0.59，其抑制NO生成之活性亦被証實具有協同作用。 本研究亦證實肉桂醛型土肉桂及錫蘭肉桂葉子精油混合配方之抗發炎活性能產生協同作用。肉桂醛型土肉桂及錫蘭肉桂葉子精油混合後能減少NF-κB蛋白表現量，且更有效減少iNOS蛋白表現量，且能提升HO-1蛋白表現，產生抗氧化之功效，進而更能抑制NO之生成，產生更有效的抗發炎作用。

Excessive inflammation will destroy the cells and tissues, and also has close relations with the developing progresses of chronic diseases. Previous studies indicated that Cinnamomum Trew. were abundant in aroma compounds and had specific bioactivities. The anti-inflammatory effect of Cinnamomum Trew. is very worthy of investigating. In this study, the LPS-induced macrophage RAW 264.7 producing nitric oxide was used as an inflammatory model for evaluating the anti-inflammatory activities of Cinnamomum osmophloeum ct. cinnamaldehyde (CO-Cin), Cinnamomum macrostemon (CM), Cinnamomum insularimontanum (CI) and Cinnamomum subavenium (CS), Cinnamomum zeylanicum (CZ), Cinnamomum burmanii (CB) and C. osmophloeum ct. linalool (CO-LL) leaf essential oils. The anti-inflammatory mechanisms of leaf essential oils from 7 Cinnamomum plants were examined according to the expressions of two inflammatory proteins, iNOS and COX-2, and the anti-oxidant protein, HO-1 by western blotting. It was demonstrated that C. osmophloeum ct. cinnamaldehyde, C. macrostemon, C. insularimontanum, and C. subavenium leaf essential oils could significantly suppress the iNOS expression and inhibited the production of NO, with the IC50 values of 13.1, 35.1, 40.2 and 41.8 μg/mL, respectively. It was proven that the C. macrostemon leaf essential oil had anti-inflammatory and anti-oxidant activities which resulted from the major constituents- E-citral and Z-citral, the two isomers which suppressed the iNOS expression and induced the HO-1 expression and their IC50 values of NO inhibition were 15.9 and 19.9 μg/mL, respectively. The mechanism of E-citral to inhibit the expression of iNOS was to suppress the NF-κB to translocate into the nuclear. Moreover, the mixture of E-citral and Z-citral with the ratio of 0.59, as they are in the essential oil of C. macrostemon leaf, was demonstrated to have a synergistic effect on inhibiting the NO production. This result obtained in this study revealed that a synergistic anti-inflammatory effect was observed by combining C. osmophloeum ct. cinnamaldehyde and C. zeylanicum essential oils. The essential oil mixture has a synergistic effect on NO inhibition for the reason that it was effective on suppressing NF-κB expression, and more effective than used alone on suppressing iNOS expression and inducing HO-1 expression.