INHIBITION OF BACTERIAL MUTAGENESIS BY CITRUS FLAVONOIDS

The antimutaqenicity of the Citrus flavonoids naringin, hesperidin, no biletin, and tangeretin against the mutagens benza[a]pyrene, 2-aminofl uorene, quercetin, and nitroquinoline N-oxide was investigated in the Salmonella/microsome assay. Naringin and hesperidin showed a weak anti mutagenic activity against benzo[a]pyrene. Tangeretin was antimutageni c against all indirectly-acting mutagens tested, but in general a larg e molar excess was necessary. Liquid preincubation increased the antim utagenicity of tangeretin against 2-aminofluorene. Nobiletin acted as an antimutagen against benzo[a]pyrene, but it enhanced the mutagenicit y of 2-aminofluorene. However, in a liquid preincubation assay nobilet in also exhibited antimutagenicity against 2-aminofluorene. Both tange retin and nobiletin inhibited the mutagenicity of quercetin. Quercetin itself acted as an antimutagen against 2-aminofluorene in a Salmonell a strain (TA1538) where its mutagenicity was not expressed. Quercetin should not merely be regarded as a genotoxic risk factor in the human diet, since its mutagenicity may be inhibited by accompanying compound s including other flavonoids, and since quercetin itself also exhibits an antimutagenic action. Because of the antimutagenic properties the Citrus flavonoids tested, especially tangeretin and nobiletin, might p lay a role in the chemoprevention of cancer.