Activity of the plant flavanol quercetin in the mouse lymphoma L5178Y TK+/- mutation, DNA single-strand break, and Balb/c 3T3 chemical transformation assays.

The activity of quercetin was investigated in (a) the L5178Y TK+/- mutation assay system, using trifluorothymidine (TFT) as the selection agent; (b) the DNA single-strand break assay L5178Y cells after the same treatment used for the mutation assay; and (c) the Balb/c 3T3 chemical transformation assay (foci method). Quercetin was active in the TK+/- mutation assay, increasing the frequency of TFT-resistant colonies from a control value of 37 per 10(6) viable cells to 355 per 10(6) viable cells at 20 micrograms/ml. When S9 was present, the activity was decreased at each concentration tested. As the S9 concentration employed (mg/ml protein) was decreased, the induced mutant frequency increased. DNA single-strand breakage was observed without S9 at 10 micrograms/ml, using the alkaline elution technique; a maximal rate of elution was reached at 20 micrograms/ml. In the chemical transformation experiments, transformation just at the level of 0.05% significance (if both intermediate and typical transformed colonies were combined) was observed. The evidence is sufficiently strong that additional attention should be given to its role as a dietary cause of human cancer.