Modulating effects of flavonoids on food mutagens in human blood and sperm samples in the comet assay

The flavonoids silymarin, myricetin, quercetin, kaempferol, rutin, and kaempferol-3-rutinoside have been examined in combination with the food mutagens 3-amino-1-methyl-5H-pyrido (4,3-b)indole (Trp) and 2-amino-3-methylimidazo-4,5-f)quinoline (IQ) in the Comet assay in human lymphocytes from donors A and B and human sperm from donor B. These compounds alone have been shown to produce positive responses in the Comet assay, as have the food mutagens. However, in combination with the food mutagens, the flavonoids produced antigenotoxic effects since DNA damage was reduced in the Comet assay in human lymphocytes and sperm over a similar dose range in the absence of metabolic activation. Only quercetin and kaempferol were examined in blood with metabolic activation, but there was no difference in response to that obtained without activation. In the blood there was an exacerbation or synergy of response at the lowest doses of the flavonoids. In the sperm this was also the case with silymarin and myricetin. With kaempferol there was no antigenotoxic effect and quercetin protected below baseline levels. Since the effects were observed in lymphocytes and sperm over a similar dose range, it would suggest that the Comet assay responses occur in somatic and germ cells in a one-to-one ratio. These results have implications for man in terms of risk assessment and in the modulation of isolated food constituents.