在美國伊利諾伊大學最近的一項研究中,科學家證實當人的結腸癌細胞暴露在一杯瑪黛茶分離出的生物活性化合物中它們會死亡。
伊利諾伊大學食品化學和食品毒理學副教授 Elvira de Mejia 說:「瑪黛茶中所含的咖啡因(又稱瑪黛因)衍生物不僅能誘導結腸癌細胞死亡,而且也能降低炎症標記物。」她說,這是非常重要的,因為炎症有可能引發癌症。
在體外研究中,Elvira de Mejia 和前研究生 Sirima Puangpraphant 從瑪黛茶中分離和純化出咖啡醯奎寧酸(Caffeoylquinic Acid, CQA)衍生物,然後用這些CQA處理人結腸癌細胞。當科學家增加CQA濃度後,癌細胞因為發生凋亡而死亡。
她說:「總而言之,癌細胞因為它的DNA遭受損傷而自我摧毀。」誘導細胞凋亡或者令細胞死亡是治療干預所有癌症類型的一種極有希望的治療策略。他們能夠鑒定出導致細胞凋亡的機制。某些CQA衍生物顯著性地降低幾種炎症標記物,這其中就包括NF-κB。它通過產生重要的酶而調節影響凋亡過程的很多基因。Elvira de Mejia說,最終癌細胞在兩種特異性酶—半胱天冬酶-3(caspase-3)和半胱天冬酶-8(caspase-8)的誘導下而死亡。
她補充道,「如果我們能夠降低NF-κB……一種將炎症和癌症連接在一起的重要性標記物……的活性,我們將更好地能夠控制正常細胞轉化為癌細胞。」這項研究結果強烈地提示著瑪黛茶中的咖啡因衍生物具有作為抗癌試劑的潛力,也可能有助於治療與炎症相關聯的其他疾病。
因為結腸及其微生物群落(Microflora)在咖啡因相關化合物的吸收和代謝中發揮著主要作用,所以瑪黛茶的抗炎症和抗癌效應在結腸中可能是非常有效的。
她又補充道,「我們相信存在足夠證據支援喝瑪黛茶是有生物活性效益的,特別是如果人們有理由擔心結腸癌的話。人們可以在健康食品店購買瑪黛茶葉袋,而且也可以在大型超市大量購買。」
科學家已經完成了喝瑪黛茶作為唯一水分來源的大鼠和只喝水的對照組大鼠患結腸癌情況的研究,也將很快把研究結果發表出來。
該文發表在美國權威營養學雜誌《Molecular Nutrition & Food Research》上。
原文摘要如下:
Dicaffeoylquinic acids in Yerba mate (Ilex paraguariensis St. Hilaire) inhibit NF-κB nucleus translocation in macrophages and induce apoptosis by activating caspases-8 and -3 in human colon cancer cells
《Molecular Nutrition & Food Research》
Volume 55, Issue 10, pages 1509–1522, October 2011
Abstract
Scope: The biological functions of caffeoylquinic acid (CQA) derivatives from various plant sources have been partially elucidated. The objectives were to isolate and purify diCQAs from Yerba mate tea leaves and assess their anti-inflammatory and anti-cancer capabilities in vitro and explore their mechanism of action.
Methods and results: Methanol extracts of dried mate leaves were resolved by flash chromatography and further purified resulting in two fractions one containing 3,4- and 3,5-diCQAs and the other 4,5-diCQA with NMR-confirmed structures. Both fractions inhibited LPS-induced RAW 264.7 macrophage inflammation by suppressing nitric oxide/inducible nitric oxide and prostaglandin E2/cyclooxygenase-2 pathways through inhibiting nucleus translocation of Nuclear factor κB subunits, p50 and p65. The diCQA fractions inhibited Human colon cancer cells CRL-2577 (RKO) and HT-29 cell proliferation by inducing apoptosis in a time- and concentration-dependent manner, but did not affect the protein levels of p21, p27, p53, and Bax:Bcl-2 ratio in RKO cells. In HT-29 cells, however, the diCQA fractions increased Bax:Bcl-2 ratio. The diCQA fractions increased the activation of caspase-8 leading to cleavage of caspase-3 in both RKO and HT-29 colon cancer cells.
Conclusion: The results suggest that diCQAs in Yerba mate could be potential anti-cancer agents and could mitigate other diseases also associated with inflammation.
(本文編譯:陶生茂,研究鏈黴菌蛋白轉運。)