Dragsted L O, Strube M, Larsen J C
National Food Agency of Denmark, Søborg.
Pharmacol Toxicol. 1993;72 Suppl 1:116-35. doi: 10.1111/j.1600-0773.1993.tb01679.x.
Cancer-protective factors are present in several fruits, vegetables and commonly used spices and herbs. They can be divided into several different groups, based on their chemical structure, e.g. polyphenols, thiols, carotenoids and retinoids, carbohydrates, trace metals, terpenes, tocopherols and degradation products of glucosinolates (i.e. isothiocyanates, indoles and dithiothiols) and others. Among each of these groups of compounds are substances, which may exert their cancer-protective action by more than one biochemical mechanism. The biochemical processes of carcinogenesis are still not known in detail and probably varies with the cancer disease in question. Accordingly, the description of the biochemical backgrounds for the actions of cancer-protective factors must be based on a simplified model of the process of carcinogenesis. The model used in this presentation is a generalised initiation-promotion-conversion model, in which initiators are thought to be directly or indirectly genotoxic, promoters are visualised as substances capable of inferring a growth advantage on initiated cells and converters are believed to be genotoxic, e.g. mutagens, clastogens, recombinogens or the like. Experimental evidence for the mechanisms of action of cancer-protective agents in fruits and vegetables that protect against initiation include the scavenging effects of polyphenols on activated mutagens and carcinogens, the quenching of singlet oxygen and radicals by carotenoids, the antioxidant effects of many compounds including ascorbic acid and polyphenols, the inhibition of activating enzymes by some flavonols and tannins, the induction of oxidation- and of conjugation (protective) enzymes by indoles, isothiocyanates and dithiothiones, the shielding of sensitive structures by some polyphenols and the stimulation of DNA-repair exerted by sulphur-containing compounds. Mechanisms at the biochemical level in anti-promotion include the antioxidant effects of carotenoids and the membrane stabilizing effects reported with polyphenols, the inhibition of proteases caused by compounds from soybeans, the stimulation of immune responses seen with carotenoids and ascorbic acid and the inhibition of ornithine decarboxylase by polyphenols and carotenoids. A few inhibitors of conversion have been identified experimentally, and it can be argued on a theoretical basis, that many inhibitors of initiation should also be efficient against conversion. The mechanisms of anticarcinogenic substances in fruits and vegetables are discussed in the light of cancer prevention and inhibition.
几种水果、蔬菜以及常用的香料和药草中存在防癌因子。根据其化学结构，它们可分为几个不同的类别，例如多酚、硫醇、类胡萝卜素和视黄醇、碳水化合物、微量金属、萜类化合物、生育酚以及硫代葡萄糖苷的降解产物（即异硫氰酸酯、吲哚和二硫醇）等。在这些化合物类别中的每一类里，都有一些物质可能通过不止一种生化机制发挥其防癌作用。致癌的生化过程仍未完全清楚，而且可能因所涉及的癌症疾病而异。因此，对防癌因子作用的生化背景的描述必须基于一个简化的致癌过程模型。本报告中使用的模型是一个广义的启动-促进-转化模型，其中启动剂被认为是直接或间接具有基因毒性的，促进剂被视为能够赋予启动细胞生长优势的物质，而转化剂被认为是具有基因毒性的，例如诱变剂、断裂剂、重组剂等。水果和蔬菜中防癌剂作用机制的实验证据表明，预防启动阶段的机制包括多酚对活化诱变剂和致癌物的清除作用、类胡萝卜素对单线态氧和自由基的猝灭作用、许多化合物（包括抗坏血酸和多酚）的抗氧化作用、一些黄酮醇和单宁对活化酶的抑制作用、吲哚、异硫氰酸酯和二硫酮对氧化酶和结合（保护）酶的诱导作用、一些多酚对敏感结构的屏蔽作用以及含硫化合物对DNA修复的刺激作用。抗促进阶段的生化水平机制包括类胡萝卜素的抗氧化作用以及多酚所报道的膜稳定作用、大豆化合物对蛋白酶的抑制作用、类胡萝卜素和抗坏血酸对免疫反应的刺激作用以及多酚和类胡萝卜素对鸟氨酸脱羧酶的抑制作用。实验已鉴定出一些转化抑制剂，并且从理论基础上可以认为，许多启动抑制剂对转化也应有效。本文根据癌症预防和抑制对水果和蔬菜中抗癌物质的作用机制进行了讨论。
