Effect of Daidzein and Genistein supplementation against oxidative injury in JURKAT T-cells and human primary lymphocytes

Different epidemiological studies on eastern population have suggested an inverse correlation between consumption of soybean products, source of isoflavones such daidzein (D) and genistein (G), and development of chronic diseases. It has been supposed that the mechanism of D and G could be related to their estrogenic or antioxidant activities although the latter has not been extensively investigated. The main objective of the present study was to evaluate the effect of daidzein and genistein against oxidative injury, before in vitro, using a leukaemia cell line (Jurkat T- cell), with D and G at concentrations between 2,5 M and 20 M, after in ex-vivo, using human primary lymphocytes separated from peripheric blood of healthy subjects, with D and G at concentration between 0,01 M and 2,5 M (concentrations reachable in plasma of consumers of foods containing isoflavones). Both in Jurkat T-cells and in primary lymphocytes after supplementation we induced oxidative stress to DNA by treatment with H2O2 500 M and to cellular membrane by treatment with Fe2+ 100 M. In Jurkat T cells are evaluated the DNA damage, by Comet assay, the lipid oxidative damage, by MDA quantification in HPLC and the modulation of the glutathione peroxidase (GPX) activity, by a spectrophotometric method. The results obtained demonstrated that: • D and G (at concentrations between 2,5 and 5 M) increased significantly the DNA protection from oxidative damage; • D (at concentrations of 2,5 and 5 M) and G (at concentrations between 2,5 and 10 M) affected significantly GPX activity; • a significant decrease of MDA production was found in cells supplemented with D (at concentration between 2,5 and 20 M). These preliminary findings support the hypothesis that isoflavones could increase cellular protection against oxidative damage, however this would seem to be dependent on concentration used. In primary lymphocytes are evaluated DNA and lipid oxidative damages. The results obtained demonstrated that: • the concentrations between 2,5 and 0,05 M of D and between 2,5 and 0,1 M of G significantly decreased oxidative damage to DNA; the concentration of 2,5 MD and G seemed to offer most protection; • the preventive effect of D and G against oxidative damage to cellular membrane has been demonstrated only with supplementation of 2,5 M. In conclusion these findings are consistent with an antioxidant activity of D and G especially with respect to DNA oxidative damage at concentrations reachable in plasma of consumers of foods containing isoflavones.