Tan B, Chu F L
Department of Food Science, Chenoweth Laboratory, University of Massachusetts, Amherst.
Am J Clin Nutr. 1991 Apr;53(4 Suppl):1071S-1075S. doi: 10.1093/ajcn/53.4.1071S.
Using benzo(a)pyrene (BaP) metabolism as a probe for chemical carcinogenesis, in vitro and in vivo effects of palm-oil carotenoid [beta-carotene (BC), alpha-carotene (AC), or canthaxanthin (CTX)] on BaP metabolism in the rat hepatic cytochrome P450-mediated monooxygenase system were studied. Apparent Michaelis-Menten constants (Km) for formation of the precursor carcinogen, 7,8-dihydrodiol BaP, were found to be 14.4 (BC), 1.74 (AC), and 0.7 (CTX) mumol/L. The order of anticarcinogenic strength established in this study was BC much greater than AC greater than CTX. Increased formation of the detoxification intermediate, 3-hydroxy BaP, with increased carotenoid concentration was observed. The order of detoxification strength was BC greater than AC = CTX. The presence of carotenoids in vivo inhibited BaP metabolism. Using 9,10-dihydrodiol BaP as an indicator for inhibition, the order of the antioxidative activity was palm oil (with carotenoids) greater than BC greater than CTX greater than palm oil (without carotenoids). BC and AC may selectively modify the rat-liver microsomal enzymes, thus providing a biochemical mechanism for the inhibitory effect of palm carotenoids on chemical carcinogenesis.
以苯并(a)芘（BaP）代谢作为化学致癌作用的探针，研究了棕榈油类胡萝卜素[β-胡萝卜素（BC）、α-胡萝卜素（AC）或角黄素（CTX）]在体外和体内对大鼠肝脏细胞色素P450介导的单加氧酶系统中BaP代谢的影响。发现前体致癌物7,8-二氢二醇BaP形成的表观米氏常数（Km）分别为14.4（BC）、1.74（AC）和0.7（CTX）μmol/L。本研究确定的抗癌强度顺序为BC远大于AC大于CTX。观察到随着类胡萝卜素浓度增加，解毒中间体3-羟基BaP的形成增加。解毒强度顺序为BC大于AC = CTX。体内类胡萝卜素的存在抑制了BaP代谢。以9,10-二氢二醇BaP作为抑制指标，抗氧化活性顺序为棕榈油（含类胡萝卜素）大于BC大于CTX大于棕榈油（不含类胡萝卜素）。BC和AC可能选择性地修饰大鼠肝脏微粒体酶，从而为棕榈类胡萝卜素对化学致癌作用的抑制效应提供一种生化机制。
