蒲公英萃取物誘發人類肝癌細胞株 HepG2 細胞凋亡之研究

Induction of Apoptosis in Human Hepatoma HepG2 Cell Line by Dandelion Extracts

張麗穎(Li-Ying Chang)

指導教授 ： 蒙美津

亞洲大學/健康學院/保健營養生技學系碩士班/碩士(2008年)

摘要

蒲公英因有利膽，利尿及抗風濕的特性，長期以來被認定為民俗藥物，也因尚有其他健康效益之故，目前在中草藥市場亦極為常見。在動物實驗中，蒲公英萃取物被證實有抗發炎的活性，而蒲公英花的區分物也具有抗氧化及細胞毒性。儘管蒲公英被視為草藥的歷史很長，但其對抗肝癌的功效著墨甚少。本研究探討蒲公英水萃取物及 70% 酒精萃取物的抗氧化及細胞毒性能力，同時以人類肝癌細胞株 HepG2 評估其誘發細胞凋亡的功效及機制。
蒲公英水萃取物及酒精萃取物在 DPPH 自由基清除率及還原力方面具有類似的功效，然而只有水萃取物有螯合亞鐵離子的能力。在總多酚化合物及類黃酮的含量上，分析結果顯示水萃取物高於酒精萃取物。藉由 trypan blue 細胞計數分析，證實蒲公英萃取物可顯著降低HepG2 細胞存活率，且其抑制能力有劑量及時間依存性的關係。此外，
經過蒲公英萃取物處理的 HepG2 細胞可觀察到細胞凋亡特徵，如：細胞皺縮、 DNA 片段化、Sub-G1 期聚積，增加 annexin V/ propidium iodide染色及 TUNEL 分析的螢光強度。在誘發細胞凋亡的過程中，給予蒲公英萃取物會導致 caspase-8 蛋白質的活化與 caspase-8 及 caspase-3mRNA 表現上的改變。
綜合上述之觀察，本研究結果顯示蒲公英萃取物同時具有抗氧化及細胞毒殺功能，而蒲公英萃取物抑制 HepG2 細胞存活的功效可能部分歸因於其植物化學成分，也可能是蒲公英萃取物為細胞凋亡的有效誘發物。

關鍵字

蒲公英 ； 人類肝癌細胞株 HepG2 ； 細胞凋亡 ； caspase-8 ； caspase-3

並列摘要

Dandelions have long been used as the folk medicine for their choleretic,diuretic and antirheumatic properties and are available today in market for a variety of health benefits. The anti-inflammatory activity of dandelion extracts has been confirmed in animal studies and dandelion flower fractions have been shown to possess both antioxidantive and cytotoxic properties.Considering the long history of the dandelion as the herb medicine, relatively little is known about their efficacy against liver cancer. In the present study,we examined the antioxidantive capabilities and cytotoxicity of aqueous and 70% ethanolic extracts（AED and EED, respectively）of dandelion as well as apoptosis induction and mechanism in human hepatoma HepG2 cell line.
Both AED and EED displayed similar patterns on DPPH scavenging activity and reducing power, while only AED exhibited ferrous ion chelating ability. The contents of total phenolic compounds and flavonoids were higher in AED as compared with those of EED.
By trypan blue assay, we demonstrated that dandelion extracts reduced viability of HepG2 cells via a dose- and time-dependent manner. Furthermore, apoptotic features such as cell shrinkage, DNA fragmentation, Sub-G1 accumulation, increased fluorescence intensities of annexin V/propidium iodide staining and TUNEL assay were observed in dandelion extracts-treated HepG2 cells. During the process of apoptosis induction, we noticed that administration of dandelion extracts resulted in the activation of caspase-8 protein and alteration of caspase-8 and caspase-3 mRNA expressions.
Taking together, our results show that dandelion extracts presented both antioxidantive and cytotoxic effects. The dandelion extracts-induced suppression of cell viability of HepG2 may in part be attributed to their phytochemical contents and as an effective inducer of apoptosis as well.

並列關鍵字

Dandelion ； human hepatoma HepG2 cell line ； apoptosis ； caspase-8 ； caspase-3

參考文獻

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