Comparison between daidzein and genistein antioxidant activity in primary and cancer lymphocytes

The main objective of this study was to compare the protective effect of daidzein and genistein against induced oxidative damage in Jurkat T-cell line and in peripheral blood lymphocytes of healthy subjects. After supplementation of cells with isoflavones (from 2.5 to 20 μmol/L in Jurkat T-cell and from 0.01 to 2.5 μmol/L in primary lymphocytes, 24 h), we determined DNA damage induced by hydrogen peroxide using the comet assay and lipid peroxidation evaluating malondialdehyde (MDA) production after ferrous ion treatment. Supplementation of Jurkat cells and primary lymphocytes with both isoflavones significantly increased DNA protection from oxidative damage at concentrations between 0.1 and 5 μmol/L (P < 0.05), and with just daidzein, at concentrations higher than 2.5 μmol/L, there was a decrease in the production of MDA (P < 0.05). Our results seem to support that daidzein is just as effective as genistein in protecting cells against oxidative damage especially with respect to DNA. Moreover, since the protective effect was found at concentrations reachable in plasma after soy consumption (less than 2 μmol/L), it can be assumed that the antioxidant activity of isoflavones could really contribute to the healthy properties of soy.