Chemoprotective glucosinolates and isothiocyanates of broccoli sprouts: metabolism and excretion in humans.
Chemoprotective glucosinolates and isothiocyanates of broccoli sprouts: metabolism and excretion in humans.
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发表时间：
2001-05
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通讯作者：
T. Shapiro;J. Fahey;K. Wade;K. Stephenson;P. Talalay
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作者：
T. Shapiro;J. Fahey;K. Wade;K. Stephenson;P. Talalay
西兰花芽含有丰富的硫代葡萄糖苷和异硫氰酸酯，它们可以诱导第二相解毒酶，提高抗氧化状态，并保护动物免受化学诱导的癌症。硫代葡萄糖苷被黑芥子酶(一种存在于植物和肠道微生物区系中的酶)水解，形成异硫氰酸酯。在体内，异硫氰酸酯与谷胱甘肽偶联，然后依次代谢为硫代尿酸。这些代谢物统称为二硫代氨基甲酸酯。我们研究了西兰花芽硫代葡萄糖酸盐和异硫氰酸盐在健康志愿者体内的处置情况。对西兰花芽进行了培养、加工和分析：(A)诱导剂效力；(B)硫代葡萄糖苷和异硫氰酸酯浓度；(C)硫代葡萄糖苷分布；以及(D)黑芥子酶活性。给药制剂包括未煮熟的新鲜芽菜(具有活性的芥子酶)以及没有芥子酶活性且仅含有硫代葡萄糖酸盐或仅含异硫氰酸酯的煮熟芽芽的匀浆。在一项交叉研究中，服用西兰花芽硫代葡萄糖酸盐或异硫氰酸盐后，尿中二硫代氨基甲酸盐的排泄量急剧增加。二硫代氨基甲酸酯在111微摩尔剂量的异硫氰酸酯的累积排泄量大于硫代葡萄糖苷的累积排泄量(分别为88.9%±5.5%和13.1%±1.9%微摩尔；P<；0.0003)。在服用四次50微摩尔剂量的异硫氰酸酯的受试者中，二硫代氨基甲酸盐排泄量的受试者内和受试者之间的差异非常小(变异系数为9%)，在递增剂量后，排泄量在25到200微摩尔的剂量范围内是线性的。彻底咀嚼完整豆芽的二硫代氨基甲酸酯排泄量高于完全吞咽(42.4+/-7.5和28.8+/-2.6微摩尔；P=0.049)。这些研究表明，异硫氰酸酯的生物利用度大约是硫代葡萄糖酸盐的6倍，硫代葡萄糖苷必须首先被水解。彻底咀嚼新鲜的芽菜会使硫代葡萄糖苷暴露在植物芥子酶中，并显著增加二硫代氨基甲酸的排泄。这些发现将有助于设计给药方案，以进行西兰花芽功效的临床研究。
Broccoli sprouts are a rich source of glucosinolates and isothiocyanates that induce phase 2 detoxication enzymes, boost antioxidant status, and protect animals against chemically induced cancer. Glucosinolates are hydrolyzed by myrosinase (an enzyme found in plants and bowel microflora) to form isothiocyanates. In vivo, isothiocyanates are conjugated with glutathione and then sequentially metabolized to mercapturic acids. These metabolites are collectively designated dithiocarbamates. We studied the disposition of broccoli sprout glucosinolates and isothiocyanates in healthy volunteers. Broccoli sprouts were grown, processed, and analyzed for (a) inducer potency; (b) glucosinolate and isothiocyanate concentrations; (c) glucosinolate profiles; and (d) myrosinase activity. Dosing preparations included uncooked fresh sprouts (with active myrosinase) as well as homogenates of boiled sprouts that were devoid of myrosinase activity and contained either glucosinolates only or isothiocyanates only. In a crossover study, urinary dithiocarbamate excretion increased sharply after administration of broccoli sprout glucosinolates or isothiocyanates. Cumulative excretion of dithiocarbamates following 111-micromol doses of isothiocyanates was greater than that after glucosinolates (88.9 +/- 5.5 and 13.1 +/- 1.9 micromol, respectively; P < 0.0003). In subjects fed four repeated 50-micromol doses of isothiocyanates, the intra- and intersubject variation in dithiocarbamate excretion was very small (coefficient of variation, 9%), and after escalating doses, excretion was linear over a 25- to 200-micromol dose range. Dithiocarbamate excretion was higher when intact sprouts were chewed thoroughly rather than swallowed whole (42.4 +/- 7.5 and 28.8 +/- 2.6 micromol; P = 0.049). These studies indicate that isothiocyanates are about six times more bioavailable than glucosinolates, which must first be hydrolyzed. Thorough chewing of fresh sprouts exposes the glucosinolates to plant myrosinase and significantly increases dithiocarbamate excretion. These findings will assist in the design of dosing regimens for clinical studies of broccoli sprout efficacy.