Water-Soluble Platinum(II) Complexes Featuring 2-Alkyl-2H-tetrazol-5-ylacetic Acids: Synthesis, Characterization, and Antiproliferative Activity

Selective anticancer activities of ruthenium(II)-tetrazole complexes and their mechanistic insights

Ruthenium-based metallotherapeutics is an interesting alternative for platinum complexes acting as anticancer agents after the entry of KP1019, NAMI-A, and TLD1339 in clinical trials. Herein, we have synthesized three new arene ruthenium(II)-tetrazole complexes viz. [Ru₂(η⁶-p-cymene)₂(2-pytz)₂Cl₂] (1), [Ru₂(η⁶-p-cymene)₂(3-pytz)Cl₃] (2), [Ru₂(η⁶-p-cymene)₂(4-pytz)Cl₃] (3) [2-pytzH = 2-pyridyl tetrazole; 3-pytzH = 3-pyridyl tetrazole; 4-pytzH = 4-pyridyl tetrazole] which have been characterized by different analytical techniques. To aid the understanding of the complex formation, reactions of the arene ruthenium(II) dimer with tetrazoles were investigated using the first principles-based Density Functional Theory (DFT) B3LYP method. Electronic structures, equilibrium geometries of the reactants and products with the first-order saddle points, reactions mechanism, the changes of enthalpy (∆H) and free energy (∆G), chemical stability, and reaction barriers of the complexes were computed using the B3LYP DFT approach. The in vitro cytotoxicity of these complexes was investigated by MTT assay on different cancer cell lines which reveal complex 2 as the most significant cytotoxic agent toward the HeLa cell line. The complexes have also shown a strong binding affinity towards CT-DNA and albumin proteins (HSA and BSA) as analyzed through spectroscopic techniques. Investigation of the mechanism of cell death by complex 2 was further performed by various staining techniques, flow cytometry, and gene expression analysis by RT-PCR. Inhibition of cell migration study has been also revealed the possibility of complex 2 to act as a prospective anti-metastatic agent.

Novel tetrazole PtII and PdII complexes with enhanced water solubility: synthesis, structural characterization and evaluation of antiproliferative activity

Novel platinum(II) and palladium(II) chlorido complexes with tetrazole derivatives 1-(2-hydroxyethyl)tetrazole (het) and 1-[tris(hydroxymethyl)methyl]tetrazole (thm), viz. cis-[Pt(het)2Cl2], trans-[Pt(het)2Cl2], trans-[Pt(thm)2Cl2], trans-[Pd(het)2Cl2], and trans-[Pd(thm)2Cl2], were synthesized. The compounds were characterized by elemental and high-resolution electrospray ionization (HRESI) mass spectrometry, high-performance liquid chromatography (HPLC), 1H, 13C and 195Pt nuclear magnetic resonance (NMR) spectroscopy, thermal analyses, and Infrared (IR) spectroscopy. Molecular and crystal structures of trans-[PdL2Cl2] and trans-[PtL2Cl2] (L = het, thm) were established by single-crystal X-ray analysis. The complex cis-[Pt(het)2Cl2] was found to undergo cis–to–trans isomerization upon heating in acetonitrile solution and in the solid state. The synthesized complexes show rather high water solubility lying in the range of 2–10 mg/L.

Tetrazole hybrids with potential anticancer activity

Cancer is one of the main causes of death throughout the world. The anticancer agents are indispensable for the treatment of various cancers, but most of them currently on the market are not specific, resulting in series of side effects of chemotherapy. Moreover, the emergency of drug-resistance towards cancers has already increased up to alarming level in the recent decades. Therefore, it's imperative to develop novel anticancer candidates with excellent activity against both drug-susceptible and drug-resistant cancers, and low toxicity as well. Tetrazole is the bioisoster of carboxylic acid, and its derivatives demonstrated promising anticancer activity. Hybridization of tetrazole with other anticancer pharmacophores may provide novel candidates with anticancer potency. The present review described the anticancer activity of tetrazole hybrids, and the structure-activity relationship (SAR) is also discussed to provide an insight for rational designs of tetrazole anticancer candidates with higher efficiency.