DNA studies of newly synthesized heteroleptic platinum(II) complexes [Pt(bpy)(iip)](2+) and [Pt(bpy)(miip)](2.)

Structural, spectroscopic, in silico, in vitro and DNA binding evaluations of tyrosyl-lysyl-threonine

The main objective of the present study is to investigate the molecular structure and DNA binding interaction of the tyrosyl-lysyl-threonine (YKT) tripeptide, which has anticancer, antioxidant and analgesic properties, using various in silico (MD, QM, molecular docking), spectroscopic (UV, FT-IR, FTIR-ATR, Raman, gel electrophoresis) and in vitro (MCF-7 and HeLa cancer cell lines and BEAS-2B cell line) methods. The optimized geometry, vibrational wavenumbers, molecular electrostatic potential (MEP), natural bond orbital (NBO) and HOMO-LUMO (highest occupied molecular orbital- lowest unoccupied molecular orbital) calculations were carried out with Density Functional Theory (DFT) using B3LYP/6-311++G(d,p) basis set to indicate conformational, vibrational and intramolecular charge transfer characteristics. The assignment of all fundamental theoretical vibration wavenumbers was performed using potential energy distribution analysis (PED). DNA is a significant pharmacological target of drugs in several diseases such as cancer. For this reason, molecular docking calculation was used to elucidate the binding and interaction between YKT tripeptide and DNA at the atomic level. Also, the dynamic behaviors of YKT and DNA was examined using MD simulations. Besides, the interaction of YKT with DNA was experimentally examined by UV titration method and agarose gel electrophoresis method. Experimental results showed that YKT was intercalatively and electrostatically bound to CT-DNA (Calf thymus DNA) and cleavage pBR322 DNA in the presence of H₂O₂. The pharmacokinetic profile of YKT was also obtained. Cytotoxic effect of YKT was evaluated on MCF-7, HeLa and BEAS-2B cell lines. Hence, these studies about YKT tripeptide may pave the way for the development of various cancer drugs. Communicated by Ramaswamy H. Sarma.

Synthesis of naphthalimide derivatives with potential anticancer activity, their comparative ds- and G-quadruplex-DNA binding studies and related biological activities

Two new cytotoxic 1,8-naphthalimide derivatives have been synthesized and characterized. Their biological activities as cytotoxicity and antimicrobial activities and inhibitory activities against DNA-polymerase were evaluated. The interactions of compounds with double-stranded- and quadruple-DNA have been studied by UV-Vis, fluorescent intercalator displacement, competition dialysis, circular dichroism and the findings were compared with the parent naphthalimide and the other compounds. The results show that both compounds (1 and 2) and the parent compound NI have strong cytotoxic activities against Beas-2B, MCF-7, HepG2 and MDA-MB-231 cancer cell lines, antimicrobial activities against Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212 and inhibitory activities towards Taq-polymerase and transcriptase. These novel cationic compounds 1 and 2 can stabilize G-quadruplexes DNA according to thermal denaturation experiments, they change the 3D structure of the DNA (see details in CD experiments) and they exhibit different binding affinities for q-DNA and ds-DNA revealed by spectrophotometric titrations and competitive dialysis studies.

The comparative study of the DNA binding and biological activities of the quaternized dicnq as a dicationic form and its platinum(II) heteroleptic cationic complex

The square-planar heteroleptic Pt(II) coordination compound [Pt(bpy)(dicnq)](NO₃)₂ (1) and the quaternized dicnq ligand, namely 12,13-dicyano-5,6-dihydrodipyrazino[2,3-f:1',2',3',4'-lmn][1,10]phenanthroline-4,7-diium dibromide (2) (Fig. 1) were synthesized and fully characterized by means of FTIR, NMR, MALDI-TOF MS and the purity was confirmed by CHN analyses. The DNA binding profiles of 1 and 2 were identified in an identical condition. The biological activities of these compounds were investigated by the assays of transcription and replication inhibition, cytotoxic and antimicrobial activity. The result of this study indicates that, both compounds strongly bind to DNA via intercalation but only 1 has a strong nuclease activity. The coordination compound of dicnq (1) binds to the DNA only slightly stronger than the quaternized form of dicnq (2), and is more potent as an inhibitor of transcription and replication and therefore, 1 has more potential as an anticancer agent but the compounds did not show cytotoxic activity against MCF-7 and MDA-MB-231 breast cancer, and DLD-1 colon cancer cell lines it was found that they only had activities against HepG2 liver cancer cell line with following IC₅₀ values; 94.75 and 159.60 µM for 1 and 2, respectively. In addition, tested bacteria are more susceptible to compound 1. These biological activities of 1 may strongly be due to its ability to digest DNA as a chemical nuclease. According to this study, the quaternization of the ligand does not make biologically more active than the coordination compound of the same ligand in this case. The compound (1) is worth further investigation for its antitumor activities.

Enantiopure copper(II) complex of natural product rosin derivative: DNA binding, DNA cleavage and cytotoxicity

To develop chiral anticancer drug candidates for molecular target DNA, the synthesis and characterization of a novel enantiomerically pure copper(II) complex [Cu 1 Cl ₂ ] (2) of an optically pure ligand N-(pyridin-2-ylmethylene) dehydroabietylamine (1) was carried out. The coordination geometry of the copper center is a distorted square-planar arrangement. The interactions of 1 and 2 with salmon sperm DNA were investigated by viscosity measurements, UV, fluorescence and circular dichroism (CD) spectroscopic techniques. All the results reveal that 1 and 2 interacted with DNA through intercalation and 2 exhibited a higher DNA binding ability. Further, 1 and 2 could cleave supercoiled pBR322 DNA by single strand and 2 displayed stronger cleavage ability in the presence of ascorbic acid. In vitro cytotoxicity of 1 and 2 against HeLa, SiHa, HepG-2 and A431 cancer cell lines was studied using CCK-8 assay. The results indicate that 2 had a superior cytotoxicity than 1 and the widely used drug cisplatin under identical conditions. Flow cytometry analysis demonstrates 2 produced death of HeLa cancer cells through an apoptotic pathway. Cell cycle analysis shows that 2 mainly arrested HeLa cells at the S phase. A novel enantiomerically pure copper(II) complex [Cu 1 Cl ₂ ] (2) of an optically pure ligand N-(pyridin-2-ylmethylene) dehydroabietylamine (1), based on natural product rosin has been synthesized. 2 has the potential to act as effective anticancer drug.