DNA/BSA binding studies and in vitro anticancer and antibacterial studies of isoelectronic Cu(I)- and Ag(I)-pyridinyl Schiff base complexes incorporating triphenylphosphine as co-ligands

Abstract

Four mononuclear Ag(I) and Cu(I) Schiff base complexes of the type [M(L)(PPh3)2]X [where M = Ag+ or Cu+, L = (E)-N-(2-fluorophenyl)-1-(pyridin-2-yl)methanimine (fpm) or (E)-1-(pyridin-2-yl)-N-(p-tolyl)methanimine (ptm) and X = NO3–] have been synthesized and characterized by various spectroscopic and analytical techniques. The analysis shows that the complexes are four-coordinates formed via the nitrogen atoms of a bidentate fpm or ptm ligands and two phosphorus atoms from the triphenylphosphine co-ligands. Two of the complexes were structurally characterized by single crystal X-ray diffraction revealing a distorted trigonal pyramidal geometry around the Ag(I) or Cu(I) center. The binding affinity of the complexes with calf thymus-DNA (CT-DNA) and bovine serum albumin (BSA) was determined using UV–visible spectroscopy. The interaction of the complexes with CT-DNA revealed the strong stacking interaction between the aromatic chromophore of the complexes and the base pairs of the CT-DNA. The study of the complexes with BSA showed moderate affinity to BSA, suggesting that complexes 1–4 can be delivered and dispositioned in vivo. Invitro anticancer activity of the synthesized complexes was evaluated against non-cancerous human embryonic kidney 293 (HEK293), cervical cancer cell (HELA), breast cancer cell (MDA-MB231) and malignant human melanoma cell (A375). High antiproliferative effects of the complexes on HELA (with EC50 values between 1.82±1.23 and 10.66±2.87 μM better than cisplatin with EC50 > 50 μM) and MDA-MB231(≈2 to 7-fold effective than cisplatin) were recorded. Further, the invitro antibacterial activity of the synthesized compounds was evaluated against S. aureus, E. coli, S. typhi and P. aeruginosa using the disc diffusion method from which the Cu(I) complexes showed better inhibitory effects than the Ag(I) complexes.