Division of Wood Cellulose, Taiwan Forestry Research Institute, Taipei, Taiwan.
Department of Laboratory Medicine, Linsen, Chinese Medicine and Kunming Branch, Taipei City Hospital, Taipei, Taiwan.
BMC Complement Med Ther. 2020 Jun 29;20(1):200. doi: 10.1186/s12906-020-02999-0.
Eucalyptus essential oils have been used in traditional medicine for centuries. It was reported that Eucalyptus leaves possess antioxidant and antimicrobial effects. Here, we investigated the anti-inflammatory activity of the essential oils extracted from the leaves of four different Eucalyptus species in RAW264.7 macrophages.
Lipopolysaccharide (LPS)-activated RAW264.7 macrophages were used to evaluate the anti-inflammatory activity of the leaf essential oils of Eucalyptus. The cell survival was quantified by an Alamar Blue assay. Nitric oxide (NO) production was assessed by Griess reaction. TNF-α and IL-6 production were measured by enzyme-linked immunosorbent assay (ELISA). Nuclear factor-κB (NF-κB) transcriptional activity was measured by NF-κB reporter assay. Intracellular protein expression levels were determined by Western blot. The expression levels of inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), mitogen-activated protein kinase (MAPK), protein kinase C (PKC) and NF-κB pathway were measured by western blot in LPS-activated RAW 264.7 macrophage.
The essential oils extracted from Eucalyptus citriodora leaf exert the best NO inhibitory activity in LPS-activated RAW264.7 macrophages. The essential oils were fractionated into fractions A-H, and fraction F has been demonstrated to inhibit the expression levels of TNF-α, IL-6, NO, iNOS and COX-2 in LPS-activated RAW264.7 macrophages. Mechanistic analysis revealed that fraction F reduced the phosphorylation levels of ERK1/2, p38, PKC-α, PKC-ε and PKC-δ, and inhibited the NF-κB transcriptional activity. The chemical composition of Fraction F was determined by GC-MS.
The discoveries made herein could help develop innovative nonsteroidal anti-inflammatory drugs with minimal side effects and strong efficacy. Clinical trials on these Eucalyptus leaf essential oils will help customize and optimize their therapeutic administration.
桉树精油在传统医学中已经使用了几个世纪。据报道，桉树叶具有抗氧化和抗菌作用。在这里，我们研究了从四种不同桉树属植物的叶子中提取的精油在 RAW264.7 巨噬细胞中的抗炎活性。
用脂多糖（LPS）激活 RAW264.7 巨噬细胞来评估桉树叶精油的抗炎活性。通过 Alamar Blue 测定法定量细胞存活率。通过 Griess 反应评估一氧化氮（NO）的产生。通过酶联免疫吸附试验（ELISA）测量 TNF-α和 IL-6 的产生。通过 NF-κB 报告基因测定法测量核因子-κB（NF-κB）转录活性。通过 Western blot 测定细胞内蛋白表达水平。通过 Western blot 测定 LPS 激活的 RAW264.7 巨噬细胞中诱导型一氧化氮合酶（iNOS）、环氧化酶-2（COX-2）、丝裂原活化蛋白激酶（MAPK）、蛋白激酶 C（PKC）和 NF-κB 通路的表达水平。
从柠檬桉叶中提取的精油在 LPS 激活的 RAW264.7 巨噬细胞中表现出最佳的 NO 抑制活性。将精油分成 A-H 馏分，馏分 F 已被证明能抑制 LPS 激活的 RAW264.7 巨噬细胞中 TNF-α、IL-6、NO、iNOS 和 COX-2 的表达水平。机制分析表明，馏分 F 降低了 ERK1/2、p38、PKC-α、PKC-ε 和 PKC-δ 的磷酸化水平，并抑制了 NF-κB 转录活性。通过 GC-MS 确定了馏分 F 的化学成分。
本文的发现有助于开发具有最小副作用和强大疗效的新型非甾体抗炎药。这些桉树叶精油的临床试验将有助于定制和优化其治疗管理。
