Most plant foods such as vegetables, fruit, seaweed and mushrooms contain antimutagenic or anticarcinogenic compounds. These compounds may be altered or lost during processing and cooking. Therefore, it is very important to investigate the change in antimutagenicity of a food due to processing and cooking. The objective of the first stage of this study was to examine the antimutagenicity of water-soluble and fat-soluble substances in plant foods. Food samples were selected from popular seasonal vegetables that are commonly available. The water-soluble fraction and fat-soluble fraction were extracted from each freeze-dried plant food with a 0.1 M phosphate buffer and methyl alcohol, respectively. The antimutagenic activity was evaluated by the Ames method to examine the mutagenicity of Trp-P-1, Trp-P-2 and 2-hydroxy- (1-N-nitrosoindolyl) propionic acid (NIHP) toward Salmonella typhimurium TA 98.
Twenty percent of the forty plant juices tested reduced the mutagenicity of Trp-P-1 by more than 50 %, and 35% of the extracts from the other 29 vegetables reduced mutagenicity of NIHP by more than 50 %. Eighty three percent of the water-soluble fractions extracted from 24 freeze-dried plant foods showed antimutagenic activity toward Trp-P-2. On the other hand, only 25% of the fat-soluble fractions from the freeze-dried plant foods showed antimutagenicity, although a few of them demonstrated very strong activity. Seventeen percent of the tested plant foods had antimutagenicity in both the water-soluble and fat-soluble fractions. Most of the plant foods tested contained antimutagens in their water-soluble fractions.