Copper (II) complex of 1,10-phenanthroline and <Emphasis Type="SmallCaps">l</Emphasis>-tyrosine with DNA oxidative cleavage activity in the gallic acid

Copper (II) complex of formulation Cu–Phen–Tyr](H₂O)](ClO₄) (Phen = 1,10-phenanthroline, l-Tyr = l-tyrosine), has been prepared, and their induced DNA oxidative cleavage activity studied. The complex binds to DNA by intercalation, as deduced from the absorption and fluorescence spectral data. Scatchard plots constructed from the absorption titration data gave binding constant 2.44 × 10⁴ M⁻¹ of base pairs. Extensive hypochromism, broadening, and red shifts in the absorption spectra were observed. Upon binding to DNA, the fluorescence from the DNA–ethidium bromide system was efficiently quenched by the copper (II) complex. Stern–Volmer quenching constant 0.61 × 10³ M⁻¹ obtained from the linear quenching plots. Cu–Phen–Tyr] complex efficiently cleave the supercoiled DNA to its nicked circular form with gallic acid as biological reductant at appropriate complex concentration. The gallic acid as reductant could observably improve copper (II) complex to DNA damage. The pseudo-Michaelis–Menten kinetic parameters (k _cat, K _M) were calculated to be 1.32 h⁻¹ and 5.46 × 10⁻⁵ M for Cu–Phen–Tyr] complex. Mechanistic studies reveal the involvement of superoxide anions and hydroxyl radical (HO^·) as the reactive species under an aerobic medium.