Identification of mutagens in Japanese pickles

A total of 108 samples of pickles, which were produced in districts with high and low incidences of stomach cancer in Japan, were extracted with methanol-chloroform. The extracts were bioassayed with Salmonella tester strains. The pickles produced in the high-cancer-incidence district were more mutagenic than those produced in the low-incidence district. The most mutagenic sample among 24 pickle specimens collected in the high-incidence district induced 130 revertants/mg of the crude extract for strain TA98. The mutagenic compounds were purified, and 2 flavonols, quercetin and rhamnetin, were identified as the major mutagens in the pickles by gas chromatography-mass spectrometry. The quantities of the 2 compounds were determined as 6.60 mg for quercetin, and 1.96 mg for rhamnetin per gram of the crude extract. The mutagenic activities of the pickles produced in the 2 districts were closely related to the amounts of quercetin in them.