Evaluation of the antimutagenic activity of different vegetable extracts using an in vitro screening test.

N-Nitroso compounds (NOC) are considered to be an important group of genotoxic carcinogens, involved in human cancer etiology. Extensive experimental and epidemiological data suggest that humans are susceptible to carcinogenesis by N-nitroso compounds. The presence of these compounds in foods may be regarded as an etiological risk factor involved in certain human cancers including cancers of the esophagus, stomach and nasopharynx [1]. Over 300 NOC have been shown to be carcinogenic in one or more animal species [2,3] and more than 40 animal species, including higher primates, are susceptible to NOC-induced carcinogenesis [4]. Druckrey et al. [5] observed that tumors induced by Nnitroso compounds in experimental animal showed similar morphological properties as tumors found in the corresponding human organs. Human exposure results via several sources (e.g. consumer products, foods, occupational exposure and tobacco consumption) at a wide range of concentrations [6]. The dietary exposure to NOC starts early in life and persists over a long period. Thus, continuous exposure to low concentrations of several Nnitroso compounds in the diet would be expected to be an etiological risk factor for certain human cancers. The formation of NOC carcinogens may result from endogenous nitrosation reaction of nitrite (one of the most widely used food additives) and amines (present in food) producing N-nitrosamines, a large group of chemical carcinogens found in different food products [7,8]. Therefore, humans are exposed not only to preformed NOC but also to a wide range of nitrogen-containing compounds and nitrosating agents that can react in vivo to form NOC. Nitrosating agents and NOC can also be synthesized endogenously in reactions mediated by bacteria and activated macrophages. Thus, endogenous formation of NOC can occur at various sites in the body [9]. On the other hand, in recent years, more attention has been dedicated to exploring compounds in foods with anti-mutagenic and anti-carcinogenic potential. Such compounds are found in almost all categories of food, fruits and vegetables being the main source [10]. Studies of dietary components such as green pepper, suggest a direct relationship between their consumption and the decrease of certain types of diseases, including cancer [11,12]. Garlic extract showed a significant antimutagenic and anticarcinogenic effect [13]. Antimutagenic activity has been also reported in cabbage, parsley, spinach, mustard green and broccoli [14]. A recent study indicated that poblano green pepper extract displays antimutagenic properties, due to the fact that some compounds present in it inhibit the endogenous nitrosation process [15]. The nitrosation reaction can be influenced by the presence of inhibitors (redox compounds such as ascorbate and vitamin E) or catalysts (metal ions, carbonyl compounds and nucleophilic anions such as Cl, I, and SCN). Plant-based food compounds can catalyze or inhibit nitrosation process depending on their structure [16]. Recognition of inhibitors of nitrosation reactions is relevant for the primary prevention of cancer. In the present study we applied the Ames test to study the anti-nitrosating properties of different vegetables commonly used in human diet, such as pumpkin, pea, string bean, purslane and bean.