荔枝(Litchi chinensis Sonn.)為無患子科(Sapindaceae)荔枝屬(Sapindaceae)植物。荔枝花開花時期為每年的3~4月,其一般以廢棄物處理。然而,我們先前的研究發現荔枝花萃取物有豐富的酚類化合物,且展現優異的抗氧化效果。因此,本研究進一步以脂多醣 (lipopolysaccharide, LPS) 誘發RAW264.7細胞株之發炎模式探討荔枝花乙醇萃取物的抗發炎功效,研究結果發現此萃取物具有抑制RAW264.7細胞發炎之抑制一氧化氮合成酶 (inducible nitric oxide synthase, iNOs)和環氧合酶-2 (cyclooxygenase-2, COX-2)的蛋白表現、白細胞介素-6 (interleukin-6, IL-6)生成,進而抑制一氧化氮 (nitric oxide, NO)和前列腺素E2 (prostagladin E2, PGE2)的生成。此荔枝花萃取物的抗發炎機制為:(1)藉由阻斷細胞核轉錄因子 (nuclear factor kappa B, NF-κB)之IKKα/β活化並抑制NF-κB P65和P50的表現;(2)在磷酸化的有絲裂原活化蛋白激酶 (mitogen-activated protein kinase, MAPKs)中,可藉由阻斷ERK之路徑,(3)與藉由阻斷白細胞介素-6 (interleukin-6, IL-6) 訊號傳遞路徑之活化JAK2和STAT3表現,達到抗發炎效果。
Litchi (Litchi chinensis Sonn.) belonging to Sapindaceae family is one of the important commercial crops in Taiwan, which blooms in late March and fruit matures in late June. The flower is usually considered as disposable byproducts. Our pervious study found that litchi flower extract had a notable amount of phenol and also exhibited good antioxidant capacity. In this study, anti-inflammation effect of ethanol extract of litchi flower was evaluated with lipopolysaccharide (LPS)-stimulated RAW264.7 cell lines further. Results show that the ethanol extract could suppress nitric oxide synthase (iNOs) and cyclooxygenase-2 (COX-2) protein expression, reduce interleukin-6 (IL-6) release, and lower nitric oxide (NO) and prostaglandin E2 (PGE2) secretion in LPS-activated RAW264.7 cells. The attenuation of LPS-induced inflammatory responses was closely related to inhibition of the inhibitor to κB kinase (IKK) α/β activation, and NF-κB P50 and P65 subunits expression (NF-κB pathway), down-regulation of phosphorylation of extracellular signal-regalation kinase (ERK) (MAPK pathway), and suppression of phosphorylation Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3) (IL-6-JAK-STAT pathway).