DNA damaging, cell cytotoxicity and serum albumin binding efficacy of the rutin-Cu(II) complex

Flavonoids are widely used as anti-oxidants, anti-cancer agents and possess metal ion chelation properties. In this report we have investigated the DNA binding (and damaging), cell cytotoxicity and serum albumin (SA) binding efficacy of the rutin-Cu(II) complex using differential spectroscopic methods. The rutin-Cu(II) complex was able to intercalate into calf thymus DNA (ct-DNA) at lower concentrations and its DNA damaging properties were also confirmed from the agarose gel based assay, fluorescence and UV-vis studies. The copper complex was found to be effective against the growth of HeLa cells in vivo. The binding constants (K-b) of the rutin-Cu(II) complex towards HSA and BSA were found to be (0.98 +/- 0.03) and (1.05 +/- 0.02) +/- 10(5) M-1, respectively, at 299 K and observed to increase with the increase in temperature. Site selectivity studies revealed that the rutin-Cu(II) complex binds near site 1 (subdomain IIA) of SAs. Thermodynamic parameters indicated that the mode of interaction of rutin and its copper complex with SAs are different from each other. Both Delta H degrees and Delta S degrees were observed to be positive for the interaction of the rutin-Cu(II) complex with SAs, indicating the presence of hydrophobic association in binding. The values of Delta H degrees were estimated to be negative (-42.07 +/- 2.92 and -23.29 +/- 2.33 kJ mol(-1) for HSA and BSA respectively) in the binding of rutin with SAs. It implies that after chelation with Cu(II) ion, rutin alters its binding mode which could have varying applications to its other physicochemical activities.