Quercetin: a mutagen, not a carcinogen, in Fischer rats.

Purified quercetin, as well as diets containing quercetin at 0.1% and 0.2%, are mutagens to Salmonella typhimurium TA100. This mutagenicity is enhanced with the S9 metabolic activation system. The urine of Fischer rats fed the 0.2% quercetin diet also is mutagenic with the S9 activation system, but the feces of these animals exhibited enhanced mutagenicity only without activation. This may indicate different quercetin metabolites in urine and feces. Rats fed these diets for 64 wk showed no consistent tissue lesions, carcinogenicity, or reproductive changes. Male rats fed 0.2% quercetin showed lowered blood serum glutamic oxaloacetic transaminase and urea nitrogen levels, but these values do not reflect pathological changes.