Synthesis, structural elucidation, biological, antioxidant and nuclease activities of some 5-Fluorouracil–amino acid mixed ligand complexes

•5-FU and amino acids form distorted octahedral with M(II) ions via bidentation.•XRD and SEM analyses show complexes are microcrystalline with uniform morphology.•Complexes prevent bacterial and fungal growth as a result of specific interactions.•Binding of complexes with CT DNA show hypochromism and red shift in absorption band.•CT DNA cleavage by Cu and Ni complexes follow Fenton’s radical oxidative mechanism.

Some biologically active mixed ligand complexes (1–9) have been synthesized from 5-Fluorouracil (5-FU; A) and amino acids (B) such as glycine (gly), l-alanine (ala) and l-valine (val) with Ni(II), Cu(II) and Zn(II) ions. The synthesized mixed ligand complexes (1–9) were characterized by various physico-chemical, spectral, thermal and morphological studies. 5-Fluorouracil and its mixed ligand complexes have been tested for their in vitro biological activities against some pathogenic bacterial and fungal species by the agar well diffusion method. The in vitro antioxidant activities of 5-Fluorouracil and its complexes have also been investigated by using the DPPH assay method. The results demonstrate that Cu(II) mixed ligand complexes (4–6) exhibit potent biological as well as antioxidant activities compared to 5-Fluorouracil and Ni(II) (1–3) and Zn(II) (7–9) mixed ligand complexes. Further, the cleaving activities of CT DNA under aerobic conditions show moderate activity with the synthesized Cu(II) and Ni(II) mixed ligand complexes (1–6) while no activity is seen with Zn(II) complexes (7–9). Binding studies of CT DNA with these complexes show a decrease in intensity of the charge transfer band to the extent of 5–15% along with a minor red shift. The free energy change values (Δ‡G) calculated from intrinsic binding constants indicate that the interaction between mixed ligand complex and DNA is spontaneous.

Graphical abstractMixed ligand complexes (1–9) have been synthesized from 5-Fluorouracil (5-FU; A) and amino acids(B) such as glycine (gly), l-alanine (ala) and l-valine (val) with Ni(II), Cu(II) and Zn(II) ions and were characterized by various physico-chemical, spectral, TG, XRD and SEM studies. They have been tested for their in vitro biological and antioxidant activities by the agar well diffusion method and the DPPH assay method respectively. The results demonstrate that Cu(II) mixed ligand complexes (4–6) exhibit higher biological as well as antioxidant activities than 5-Fluorouracil and their counterparts, Ni(II) (1–3) and Zn(II) (7–9) mixed ligand complexes. The cleavage activity of CT DNA under aerobic condition reveals moderate activity with Cu(II) and Ni(II) mixed ligand complexes (1–6) while Zn(II) complexes (7–9) show no activity. Binding studies of CT DNA with these complexes show 5–15% of hypochromicity and a minor red-shift in the charge transfer band. The negative free energy change values (Δ‡G) calculated for the binding indicate that the mixed ligand complexes can interact with DNA in a spontaneous manner.Figure optionsDownload full-size imageDownload as PowerPoint slide