| Abstract: | 抱子甘藍屬十字花科之植物，無論在動物或人體實驗都顯示防癌效果，且其機轉是透過對肝臟解毒系統活化而加速致癌物之代謝。而此防癌效果是因抱子甘藍中glucosinolate之裂解產物所造成，其主要由抱子甘藍中myrosinase催化產生，所以一旦加熱，抱子甘藍中此酵素活性及肝臟解毒系統活化機轉即被抑制。本實驗欲進一步探討加熱處理之抱子甘藍對phase Ⅰ與phase Ⅱ解毒酵素活性之影響差異，實驗分三組，抱子甘藍(1)冷凍乾燥組（glucosinolate未裂解）(2)加熱冷凍乾燥組（裂解酵素已破壞）(3)半量之裂解冷凍乾燥組（glucosinolate已裂解），(4)and 0.5% ethoxyquin diet (EQ) was used as a positive control以2%重量混合成飼料，餵以小白鼠（4隻／組）7天，結果發現，在第(2)組小白鼠GST (phase Ⅱ酵素）活性顯著上升，顯示在植物裂解酵素不存在之狀況下，腸胃道之微生物仍可促進裂解反應，但由CYP1A （phase Ⅰ酵素）活性增加不顯著（僅1.4倍）看來，根據定義：單獨phase Ⅱ酵素活性增加，為monofunctional induction/inducer，可加速致癌物之代謝。而phase Ⅰ與phase Ⅱ酵素活性同時增加，稱之bifunctional induction/inducer，反可能有致癌性，我們假設：第(2)組小白鼠所攝取之加熱冷凍乾燥之抱子甘藍之monofunctional inducer仍可被裂解出並在腸胃道被吸收造成phase Ⅱ酵素活性上升。相反的，我們先前實驗顯示抱子甘藍中之bifunctional inducer，如Ⅰ-3-C，加熱後直到腸道才被分解出來，除錯失正常情形下在口腔之裂解，及在胃酸化而被活化之機會，因而無法造成induction，所以我們推測，經由加熱可去除抱子甘藍可能致癌之bifunctional induction效用，因而加強了抱子甘藍之健康效益。
Brussels sprouts, a cruciferous vegetable, have been shown to have chemopreventive effects in both animals and humans. The mechanism behind this chemopreventive activity may be associated with the induction of drug-metabolizing enzymes which modulate the metablosim of carcinogens/the carcinogen metabolism. Once the plant is damaged by chewing, however, conversion of breakdown products from parent glucosinolates (GS) in Brussels sprouts is triggered by myrosinase (EC 3.2.3.1), which can be inhibited by heating. In this study, we investigate the heat-induced inhibition of drug-metabolizing enzyme activity in mice fed with freeze-dried, heated freeze-dried or half amount autolyzed freeze-dried Brussels sprouts powder. 0.5% ethoxyquin diet (EQ) was fed to another group of mice as a positive control. The study mice, four per group, were fed a diet consisting of 20% Brussels sprouts (w/w) for 7 days. Each group had its own pair-fed group. We found significantly greater inductions of glutathione S- transferase (GST), quinine reductase (QR), and phase Ⅱ drug-metabolizing enzyme activities in groups fed within freeze-dried and heated freeze-dried Brussels sprouts than their pair-fed groups. These findings indicate that intestinal microflora still can hydrolyze glucosinolates without plant myrosinase activity, though the alteration of cytochrome- P-450 1A (CYP1A, a phase Ⅰ drug-metabolizing enzyme) induction was only 1.4-fold. Therefore, assuming that bifunctional induction increases both phase Ⅰ and phase Ⅱ enzyme activities and that monofunctional induction increases phase Ⅱ alone, we hypothesize in the case of heated Brussels sprouts powder, hydrolyzed monofuctional inducers created/produced by microflora can be formed and absorbed in the intestine, causing the induction of phase Ⅱ enzymes/enzyme activities. In contrast, in a previous study bifunctional inducers, such as indole-3-carbinol (Ⅰ-3-C) which has not broken down yet for acid condensation for activating in stomach, cannot function. Hence, heating may decrease hepatic bifunctional inductions which could normally bioactivate carcinogen and, therefore, improve the health benefits derived from Brussels sprouts. |
