| 摘要: | 根據行政院衛生署的統計資料，1982年起惡性腫瘤為台灣十大死亡原因之首。由天然物找尋預防癌症藥物及抗癌藥物，解決多重抗藥性造成的化療失效是非常重要之課題。山竹 (Garcinia mangostana) 是著名的亞洲熱帶水果，其成分 γ-mangostin 是一種從果殼中分離的 xanthone 衍生物，在我們過去的研究中，已經確認 γ-mangostin 具有抗發炎、抗癌以及抗氧化的作用。以 MTT 分析細胞株之增生，發現 γ-mangostin 對 HepG2、HT-29、U-87 MG 和 GBM 8401 細胞具有抑制增生的作用並呈現濃度依存性及時間依存性；以 Giemsa stain 觀察細胞型態，細胞之鏡檢反應結果，也發現 γ-mangostin 誘導細胞染色質皺縮、凋亡小體形成，展現細胞凋亡的特徵；以 PI 分析細胞週期，結果發現 γ-mangostin 處理 HepG2、HT-29、U-87 MG 及 GBM 8401 細胞，hypodiploid cells 有增加的趨勢；另外，以 DiOC6(3) 和 DCFDA 染色之粒線體膜電位變化及細胞中 ROS 的變化，結果也發現 γ-mangostin 作用使得 ROS 產生，造成粒線體膜電位 (ΔΨm) 的下降，進而誘導細胞凋亡的發生。進一步分析 γ-mangostin 抑制 FeCl2 及 Fe(NH4)2(SO4)2 ‧ 6H2O 誘導 SD 大鼠肝或腦粒線體脂質過氧化，使用 TBARS 方法及 HPLC 定量MDA(TBA)2的生成，結果顯示，γ-mangostin 抑制 SD 大鼠肝或腦粒線體脂質過氧化之 IC50 分別為 6.96 μM 及 39.55 μM；而 γ-mangostin 主要藉由提供氫原子，以達到清除 DPPH 自由基之效果，其 IC50 為20.38 ± 0.84 μM；另一方面 γ-mangostin 與 Fe2+ 結合，減少 ferrozine- Fe2+ 的生成，因此也具有螯合亞鐵離子的效果；但對於清除超氧陰離子及過氧化氫並沒有顯著的效果。綜合上述結果，證實 γ-mangostin 對 HepG2、HT-29、U-87 MG 及 GBM 8401 四種癌細胞皆具有抑制細胞增生的作用，並誘導癌細胞走向細胞凋亡，也可以抑制Fe2+ 引起的氧化逆境 (oxidative stress)，對 FeCl2 及Fe(NH4)2(SO4)2 ‧ 6H2O 誘導肝和腦粒線體之脂質過氧化具有抑制的作用，且具有清除 DPPH 自由基之能力，進一步減少組織損傷和癌症的形成。這些證據顯示，γ-mangostin可作為肝癌、大腸直腸癌和腦癌預防癌症的植物化學成分，並可發展作為抗腫瘤之潛在的先導化合物。
Since 1982, malignant tumors are the first of the ten leading causes of death in Taiwan according to the data from Department of Health, Executive Yuan. For the multiple drugs resistant of cancer chemotherapy, development of effect agents from natural products is one of the important issues to treatment malignant tumors in the future. Mangosteen (Garcinia mangostana) is a famous Asian tropical fruit. γ-Mangostin is a xanthone derivative isolated from the fruit hull. In our previous studies, we found evidence of anti-inflammatory, anti-tumor, and antioxidant activities in γ-mangostin. Cell viability was determined by MTT assay, and γ-mangostin showed concentration- and time-dependent antiproliferative activities on HepG2, HT-29, U-87 MG and GBM 8401 cells. Microscopic observations under Giemsa staining showed that γ-mangostin induced nuclear condensation and the appearance of apoptotic bodies, characteristics of apoptosis in HepG2, HT-29, U-87 MG and GBM 8401 cells. In addition, flow cytometry analysis showed increases of hypodiploid cells with an enhancement of intracellular peroxide production was detected in γ-mangostin-treated cells via PI staining, DCFDA assay and DiOC6(3) staining. We performed further studies to assess the lipid peroxidation (LPO) inhibition of γ-mangostin. FeCl2 and Fe(NH4)2(SO4)2‧6H2O induced liver or brain mitochondria LPO on SD rat was determined by a TBARS, and the MDA(TBA)2 product was quantitatively analyzed by HPLC. The half maximal inhibitory concentration (IC50) of γ-mangostin for LPO on SD rat liver mitochondria and brain mitochondria were 6.96 μM and 39.55 μM, respectively. The IC50 of γ-mangostin was 20.38 μM on DPPH scavenging capability. In addition, γ-mangostin had chelating effect on ferrous ions, but no significant effect on superoxide anion radical and hydrogen peroxide scavenging. These results supported that γ-mangostin processed activity to inhibit LPO, sacveng DPPH, and induce apoptosis in HepG2, HT-29, U-87 MG and GBM 8401 cells. It suggests that γ-mangostin is an effective phytochemical with benefic activity to treat several different cancers include liver, colon and brain cancer, and may play as a potential lead compound for future anti-cancer drug development. |
