Chung F L, Jiao D, Getahun S M, Yu M C
Division of Carcinogenesis and Molecular Epidemiology, American Health Foundation, Valhalla, New York 10595, USA.
Cancer Epidemiol Biomarkers Prev. 1998 Feb;7(2):103-8.
Isothiocyanates (ITCs) are a family of biologically active compounds that are distributed widely in cruciferous vegetables. Although studies in rodents have shown that these compounds are effective and versatile inhibitors of tumorigenesis, the role of dietary ITCs in the protection against human cancers remains to be established. A prerequisite of human studies is to develop an uptake biomarker for dietary ITCs. In this study, we describe a rapid high-performance liquid chromatography-based assay to measure the total ITC level in human urine. This assay is based on a previously described reaction of ITCs or their thiol conjugates with 1,2-benzenedithiol to yield a cyclocondensation product, 1,3-benzodithiole-2-thione, which then can be quantified by reverse phase high-performance liquid chromatography with UV detection. This new assay was validated by analyzing urine samples from 14 subjects who had consumed a known amount of watercress or brown mustard in a controlled experiment. The N-acetylcysteine conjugates of phenethyl ITC and allyl ITC from watercress and brown mustard, respectively, were quantified and compared with the results obtained from the current assay. Results of the two methods were highly correlated (r = 0.978), indicating the specificity of this new assay for dietary ITCs. The feasibility of this assay for population-based studies was examined using stored urine samples collected from nine participants of a prospective cohort study in Shanghai, China, who indicated that they were daily consumers of dark green vegetables. There was a 10-fold variation in urinary ITC contents among these samples, ranging from 0.7 to 7.0 micromol/g creatinine. These results show the potential use of this uptake biomarker in epidemiological studies to identify the role of dietary ITCs in modifying cancer risks in humans.
异硫氰酸盐（ITCs）是一类生物活性化合物，广泛分布于十字花科蔬菜中。尽管对啮齿动物的研究表明，这些化合物是肿瘤发生的有效且多功能抑制剂，但膳食ITCs在预防人类癌症中的作用仍有待确定。人体研究的一个前提是开发一种膳食ITCs的吸收生物标志物。在本研究中，我们描述了一种基于高效液相色谱的快速测定方法，用于测量人尿中的总ITC水平。该测定方法基于先前描述的ITCs或其硫醇共轭物与1,2-苯二硫醇反应生成环缩合产物1,3-苯并二硫杂环戊烯-2-硫酮，然后可以通过反相高效液相色谱结合紫外检测进行定量。通过分析14名受试者在对照实验中食用了已知量的西洋菜或黄芥末后的尿液样本，验证了这种新的测定方法。分别对西洋菜和黄芥末中的苯乙基ITC和烯丙基ITC的N-乙酰半胱氨酸共轭物进行了定量，并与当前测定方法得到的结果进行了比较。两种方法的结果高度相关（r = 0.978），表明这种新测定方法对膳食ITCs具有特异性。使用从中国上海一项前瞻性队列研究的9名参与者收集的储存尿液样本，检验了该测定方法在基于人群的研究中的可行性，这些参与者表示他们每天都食用深绿色蔬菜。这些样本中尿ITC含量存在10倍差异，范围为0.7至7.0微摩尔/克肌酐。这些结果表明，这种吸收生物标志物在流行病学研究中具有潜在用途，可用于确定膳食ITCs在改变人类癌症风险中的作用。
