Browsing by Author "Bhuvanesh, Nattamai"

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    Spectroscopic, anticancer and antioxidant studies of fluxional trans-[PdCl2(S-acylthiourea)2] complexes
    (Elsevier B.V., 2021-07-19) Dorairaj, Dorothy Priyanka; Haribabu, Jebiti; Chithravel, Vadivalagan; Vennila, Kailasam N; Bhuvanesh, Nattamai; Echeverria, Cesar; Hsu, Sodio C.N.; Karvembu, Ramasamy
    A library of palladium(II) acylthiourea complexes (1–6) of the type [PdCl2{C8H13N2OS(R)}2] [where R = C6H4CH3(o) (1), C6H5 (2), C6H4OCH3(p) (3), C6H4OC2H5(p) (4), C10H7 (5) or C6H5Cl(p) (6)] was synthesized and characterized by UV–Visible, FT-IR, 1H NMR, 13C NMR and ESI-Mass spectroscopy, and elemental analysis. Single crystal X-ray structure of complex 4 revealed the monodentate coordination of acylthiourea ligand through sulphur atom to the palladium ion in a trans fashion. In addition, variable-temperature (VT) NMR studies were performed to analyze the fluxional nature of complexes. The interaction of complexes with calf thymus (CT) DNA and BSA (bovine serum albumin) was analyzed by spectroscopic and molecular docking studies. The results inferred intercalation binding mode of the complexes with DNA. All the complexes exhibited good binding with BSA as well. Further, the complexes were found to act as good scavengers of DPPH as deduced from the antioxidant assay. In vitro cytotoxicity of the compounds against A549 (lung) cancer and HEK293 (human embryonic kidney) normal cell lines was investigated by MTT assay. Among the six complexes, complex 5 bearing a napthyl substitution in acylthiourea exhibited a remarkable activity against A549 cell line with an IC50 value of 14.8 µM and was more active than cisplatin (IC50 = 17.8 µM). On the other hand, it showed less toxicity on HEK293 cell line. The cell death mechanism was analyzed by AO/EB and DAPI staining, flow cytometry and Western blot investigations, which revealed that complex 5 could initiate cell death through apoptosis.
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    Synthesis of sulfanyl derivatives of 1,2,4-triazoles via an acid catalyzed intramolecular cyclization of isothiosemicarbazones: structural characterization, E/Z isomerism, mechanistic insights and in vitro cytotoxicity
    (Royal Society of Chemistry, 2026-03-10) Snisha, Kallivalappil; Karthikeyan, Mano Chitra; Bhuvanesh, Nattamai; Arockiam, Antony Joseph Velanganni; Karvembu, Ramasamy
    Sulfanyl derivatives of 1,2,4-triazoles (CL1–CL3) were synthesized via a Lewis or Brønsted acid catalyzed intramolecular cyclization of corresponding isothiosemicarbazones (TL1–TL3). All the synthesized isothiosemicarbazones and their cyclized sulfanyl 1,2,4-triazole derivatives were well characterized by spectroscopic techniques and single crystal XRD analyses. The E/Z isomerism of the isothiosemicarbazones was elucidated using NMR spectroscopy and single crystal XRD analysis. Mechanistic investigations, supported by controlled experiments and spectroscopic evidence, revealed that the cyclization proceeded via an ionic pathway with the evolution of hydrogen. The cytotoxic effect of the cyclized sulfanyl 1,2,4-triazole derivatives (CL1–CL3) was evaluated by MTT assay against MDA-MB-231 (breast), MCF-7 (breast), and HeLa (cervical) cancer cell lines, as well as HEK-293 (kidney) normal cell line, taking 5-fluorouracil (5-FU) as a reference drug. All the substituted sulfanyl-1,2,4-triazoles showed higher cytotoxicity toward MDA-MB-231 and HeLa cells than 5-FU, while exhibiting low toxicity toward HEK-293 cells, indicating good selectivity toward cancer cells. Substituted compounds [CL2 (p-OCH3) and CL3 (p-NO2)] displayed enhanced activity compared to the unsubstituted one (CL1), indicating the influence of the substituents on cytotoxicity. Fluorescence staining assays (AO/EB, Hoechst 33342, Rhodamine 123 and DCFH-DA) further supported the observed cytotoxic effects, and suggested that the compounds promoted apoptotic cell death via intracellular reactive oxygen species (ROS) generation, depletion of mitochondrial membrane potential (MMP) and damage to nuclear material.