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Dembitsky VM. Steroids Bearing Heteroatom as Potential Drugs for Medicine. Biomedicines 2023; 11:2698. [PMID: 37893072 PMCID: PMC10604304 DOI: 10.3390/biomedicines11102698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 09/27/2023] [Accepted: 09/28/2023] [Indexed: 10/29/2023] Open
Abstract
Heteroatom steroids, a diverse class of organic compounds, have attracted significant attention in the field of medicinal chemistry and drug discovery. The biological profiles of heteroatom steroids are of considerable interest to chemists, biologists, pharmacologists, and the pharmaceutical industry. These compounds have shown promise as potential therapeutic agents in the treatment of various diseases, such as cancer, infectious diseases, cardiovascular disorders, and neurodegenerative conditions. Moreover, the incorporation of heteroatoms has led to the development of targeted drug delivery systems, prodrugs, and other innovative pharmaceutical approaches. Heteroatom steroids represent a fascinating area of research, bridging the fields of organic chemistry, medicinal chemistry, and pharmacology. The exploration of their chemical diversity and biological activities holds promise for the discovery of novel drug candidates and the development of more effective and targeted treatments.
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Affiliation(s)
- Valery M Dembitsky
- Centre for Applied Research, Innovation and Entrepreneurship, Lethbridge College, 3000 College Drive South, Lethbridge, AB T1K 1L6, Canada
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Cseh K, Berasaluce I, Fuchs V, Banc A, Schweikert A, Prado-Roller A, Hejl M, Wernitznig D, Koellensperger G, Jakupec MA, Kandioller W, Malarek MS, Keppler BK. Anticancer Tungstenocenes with a Diverse Set of ( O,O-), ( O, S-) and ( O, N-) Chelates-A Detailed Biological Study Using an Improved Evaluation via 3D Spheroid Models. Pharmaceutics 2023; 15:1875. [PMID: 37514061 PMCID: PMC10384408 DOI: 10.3390/pharmaceutics15071875] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Revised: 06/15/2023] [Accepted: 06/25/2023] [Indexed: 07/30/2023] Open
Abstract
The synthesis, characterization and biological activity of tungstenocenes with varying biologically active (O,O-), (S,O-) and (N,O-) chelates are described. Complexes were characterized by 1H and 13C NMR, elemental analysis, ESI-mass spectrometry, FT-IR spectroscopy and X-ray diffraction analysis. The aqueous stability was studied by UV/Vis spectroscopy and the WIV to WV process by cyclic voltammetry. The cytotoxicity was determined by the MTT assay in A549, CH1/PA-1 and SW480 cancer cells as well as in IMR-90 human fibroblasts. Extensive biological evaluation was performed in three other human cancer cell lines (HCT116, HT29 and MCF-7) in monolayer and multicellular tumor spheroid cultures to better understand the mode of action. Lead compounds showed promising in vitro anticancer activity in all cancer cell lines. Further studies yielded important insights into apoptosis induction, ROS generation, different patterns in metal distribution (detected by LA-ICP-TOF-MS), changes in KI67 (proliferation marker) expression and DNA interactions. The results based on qualitative and quantitative research designs show that complexes containing (S,O-) chelates are more active than their (O,O-) and (N,O-) counterparts. The most striking results in spheroid models are the high antiproliferative capacity and the different distribution pattern of two complexes differing only in a W-S or W-O bond.
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Affiliation(s)
- Klaudia Cseh
- Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Straße 42, A 1090 Vienna, Austria
| | - Iker Berasaluce
- Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Straße 42, A 1090 Vienna, Austria
| | - Valentin Fuchs
- Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Straße 42, A 1090 Vienna, Austria
| | - Alexandra Banc
- Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Straße 42, A 1090 Vienna, Austria
| | - Andreas Schweikert
- Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Straße 42, A 1090 Vienna, Austria
- Institute of Analytical Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Straße 38, A 1090 Vienna, Austria
| | - Alexander Prado-Roller
- Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Straße 42, A 1090 Vienna, Austria
| | - Michaela Hejl
- Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Straße 42, A 1090 Vienna, Austria
| | - Debora Wernitznig
- Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Straße 42, A 1090 Vienna, Austria
| | - Gunda Koellensperger
- Institute of Analytical Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Straße 38, A 1090 Vienna, Austria
| | - Michael A Jakupec
- Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Straße 42, A 1090 Vienna, Austria
- Research Cluster "Translational Cancer Therapy Research", University of Vienna, Waehringer Straße 42, A 1090 Vienna, Austria
| | - Wolfgang Kandioller
- Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Straße 42, A 1090 Vienna, Austria
- Research Cluster "Translational Cancer Therapy Research", University of Vienna, Waehringer Straße 42, A 1090 Vienna, Austria
| | - Michael S Malarek
- Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Straße 42, A 1090 Vienna, Austria
| | - Bernhard K Keppler
- Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Straße 42, A 1090 Vienna, Austria
- Research Cluster "Translational Cancer Therapy Research", University of Vienna, Waehringer Straße 42, A 1090 Vienna, Austria
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Fernandez-Vega L, Ruiz Silva VA, Domínguez-González TM, Claudio-Betancourt S, Toro-Maldonado RE, Capre Maso LC, Ortiz KS, Pérez-Verdejo JA, González JR, Rosado-Fraticelli GT, Meléndez FP, Betancourt Santiago FM, Rivera-Rivera DA, Navarro CM, Bruno Chardón AC, Vera AO, Tinoco AD. Evaluating Ligand Modifications of the Titanocene and Auranofin Moieties for the Development of More Potent Anticancer Drugs. INORGANICS 2020; 8. [PMID: 34046448 PMCID: PMC8152503 DOI: 10.3390/inorganics8020010] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Over time platinum-based anticancer drugs have dominated the market, but their side effects significantly impact the quality of life of patients. Alternative treatments are being developed all over the world. The titanocene and auranofin families of compounds, discovered through an empirical search for other metal-based therapeutics, hold tremendous promise to improve the outcomes of cancer treatment. Herein we present a historical perspective of these compounds and review current efforts focused on the evolution of their ligands to improve their physiological solution stability, cancer selectivity, and antiproliferative performance, guided by a clear understanding of the coordination chemistry and aqueous speciation of the metal ions, of the cytotoxic mechanism of action of the compounds, and the external factors that limit their therapeutic potential. Newer members of these families of compounds and their combination in novel bimetallic complexes are the result of years of scientific research. We believe that this review can have a positive impact in the development and understanding of the metal-based drugs of gold, titanium, and beyond.
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Sagnou M, Mavroidi B, Shegani A, Paravatou-Petsotas M, Raptopoulou C, Psycharis V, Pirmettis I, Papadopoulos MS, Pelecanou M. Remarkable Brain Penetration of Cyclopentadienyl M(CO)3+ (M = 99mTc, Re) Derivatives of Benzothiazole and Benzimidazole Paves the Way for Their Application as Diagnostic, with Single-Photon-Emission Computed Tomography (SPECT), and Therapeutic Agents for Alzheimer’s Disease. J Med Chem 2019; 62:2638-2650. [DOI: 10.1021/acs.jmedchem.8b01949] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Chen C, Ye Y, Wang R, Zhang Y, Wu C, Debnath SC, Ma Z, Wang J, Wu M. Streptomyces nigra sp. nov. Is a Novel Actinobacterium Isolated From Mangrove Soil and Exerts a Potent Antitumor Activity in Vitro. Front Microbiol 2018; 9:1587. [PMID: 30072967 PMCID: PMC6058180 DOI: 10.3389/fmicb.2018.01587] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 06/26/2018] [Indexed: 12/19/2022] Open
Abstract
A new bacterial strain, designated 452T, was isolated from the rhizosphere soil of the mangrove Avicennia marina in China. As determined, its cell wall peptidoglycan contained LL-diaminopimelic acid; MK-9(H8) and MK-9(H6) were the major isoprenoid quinones; and iso-C16:0 (31.3%), anteiso-C15:0 (16.9%), and iso-C15:0 (12.5%) were the major cellular fatty acids (>10.0%). Phylogenetic analysis based on the 16S rRNA gene sequence revealed that strain 452T formed a distinct lineage in the clade of the genus Streptomyces, and was closely related to S. coerulescens DSM 40146T (99.6% sequence identity), S. bellus DSM 40185T (99.5%), and S. coeruleorubidus DSM 41172T (99.3%). The DNA-DNA relatedness between strain 452T and these type strains ranged between 29.3 and 42.3%. Based on the phenotypic, chemotaxonomic, and phylogenetic features, the strain 452T is considered to represent a novel species of the genus Streptomyces, for which the name Streptomyces nigra sp. nov. is proposed. The type strain is 452T (=KCTC 39960T = MCCC 1K03346T). Further, strain 452T extracts exhibited a pronounced antitumor activity against human cancer cell lines A549, HCT-116, and HepG2, but not against normal human colon cells CCD-18Co. Active substances in the fermentation broth of strain 452T were isolated by bioassay-guided analysis, and then purified using a macroporous resin, silica gel, sephadex LX-20 column, and semi-preparative high-performance liquid chromatography (HPLC). Eight proline-containing diketopiperazines, namely, cyclo(Pro-Ala), cyclo(Pro-Gly), cyclo(Pro-Phe), cyclo(Pro-Met), cyclo(Pro-Val), cyclo(Pro-Leu), cyclo(Pro-Tyr), and cyclo(L-Leu-trans-4-hydroxy-L-Pro), were identified by electrospray ionization mass spectrometry (MS) and nuclear magnetic resonance (NMR). The compounds displayed different levels of cytotoxicity. The highest cytotoxicity was exhibited by cyclo(Pro-Ala) and cyclo(Pro-Met) against A549 cells, and cyclo(Phe-Pro) and cyclo(Pro-Ala) against HCT-116 cells, with average IC50 values equal to 18.5, 27.3, 32.3, and 47.6 μg/mL, respectively. The diversity of diketopiperazines and other chemicals produced by 452T was further investigated using gas chromatography (GC)-MS and liquid chromatography (LC)-MS. The analysis revealed 16 types of metabolites with antitumor activity and 16 other types of diketopiperazines. Hence, extracts of the newly identified strain may be used a starting material for the development of antitumor agents.
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Affiliation(s)
- Can Chen
- Laboratory of Marine Microbial Resources Utilization, Ocean College, Institute of Marine Biology, Zhejiang University, Hangzhou, China
| | - Yanghui Ye
- Laboratory of Marine Microbial Resources Utilization, Ocean College, Institute of Marine Biology, Zhejiang University, Hangzhou, China
| | - Ruijun Wang
- Laboratory of Marine Microbial Resources Utilization, Ocean College, Institute of Marine Biology, Zhejiang University, Hangzhou, China
| | - Yinglao Zhang
- Biomedical Research Program, School of Life Sciences, Anhui Agricultural University, Hefei, China
| | - Chen Wu
- Institute of Hydraulic and Marine Engineering, School of Hydraulic and Environmental Engineering, Zhejiang University of Water Resources and Electric Power, Hangzhou, China
| | - Sanjit C Debnath
- Laboratory of Marine Microbial Resources Utilization, Ocean College, Institute of Marine Biology, Zhejiang University, Hangzhou, China
| | - Zhongjun Ma
- Laboratory of Marine Microbial Resources Utilization, Ocean College, Institute of Marine Biology, Zhejiang University, Hangzhou, China
| | - Jidong Wang
- Department of New Drug Screening, Zhejiang Hisun Pharmaceutical Co., Ltd., Taizhou, China
| | - Min Wu
- Laboratory of Marine Microbial Resources Utilization, Ocean College, Institute of Marine Biology, Zhejiang University, Hangzhou, China
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Dembitsky VM, Gloriozova TA, Imbs AB. Ferrocene and titanocene steroid conjugates: Structures and activities - a brief review. VIETNAM JOURNAL OF CHEMISTRY 2018. [DOI: 10.1002/vjch.201800001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
| | | | - Andrew B. Imbs
- National Scientific Center of Marine Biology; Vladivostok Russia 690041
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Loza-Rosas SA, Vázquez-Salgado AM, Rivero KI, Negrón LJ, Delgado Y, Benjamín-Rivera JA, Vázquez-Maldonado AL, Parks TB, Munet-Colón C, Tinoco AD. Expanding the Therapeutic Potential of the Iron Chelator Deferasirox in the Development of Aqueous Stable Ti(IV) Anticancer Complexes. Inorg Chem 2017; 56:7788-7802. [PMID: 28644630 PMCID: PMC5557045 DOI: 10.1021/acs.inorgchem.7b00542] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The recent X-ray structure of titanium(IV)-bound human serum transferrin (STf) exhibiting citrate as a synergistic anion reveals a difference in Ti(IV) coordination versus iron(III), the metal endogenously delivered by the protein to cells. This finding enriches our bioinspired drug design strategy for Ti(IV)-based anticancer therapeutics, which applies a family of Fe(III) chelators termed chemical transferrin mimetic (cTfm) ligands to inhibit Fe bioavailability in cancer cells. Deferasirox, a drug used for iron overload disease, is a cTfm ligand that models STf coordination to Fe(III), favoring Fe(III) binding versus Ti(IV). This metal affinity preference drives deferasirox to facilitate the release of cytotoxic Ti(IV) intracellularly in exchange for Fe(III). An aqueous speciation study performed by potentiometric titration from pH 4 to 8 with micromolar levels of Ti(IV) deferasirox at a 1:2 ratio reveals exclusively Ti(deferasirox)2 in solution. The predominant complex at pH 7.4, [Ti(deferasirox)2]2-, exhibits the one of the highest aqueous stabilities observed for a potent cytotoxic Ti(IV) species, demonstrating little dissociation even after 1 month in cell culture media. UV-vis and 1H NMR studies show that the stability is unaffected by the presence of biomolecular Ti(IV) binders such as citrate, STf, and albumin, which have been shown to induce dissociation or regulate cellular uptake and can alter the activity of other antiproliferative Ti(IV) complexes. Kinetic studies on [Ti(deferasirox)2]2- transmetalation with Fe(III) show that a labile Fe(III) source is required to induce this process. The initial step of this process occurs on the time scale of minutes, and equilibrium for the complete transmetalation is reached on a time scale of hours to a day. This work reveals a mechanism to deliver Ti(IV) compounds into cells and trigger Ti(IV) release by a labile Fe(III) species. Cellular studies including other cTfm ligands confirm the Fe(III) depletion mechanism of these compounds and show their ability to induce early and late apoptosis.
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Affiliation(s)
- Sergio A. Loza-Rosas
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, Río Piedras, Puerto Rico 00931, United States
| | - Alexandra M. Vázquez-Salgado
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, Río Piedras, Puerto Rico 00931, United States
| | - Kennett I. Rivero
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, Río Piedras, Puerto Rico 00931, United States
| | - Lenny J. Negrón
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, Río Piedras, Puerto Rico 00931, United States
| | - Yamixa Delgado
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, Río Piedras, Puerto Rico 00931, United States
| | - Josué A. Benjamín-Rivera
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, Río Piedras, Puerto Rico 00931, United States
| | - Angel L. Vázquez-Maldonado
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, Río Piedras, Puerto Rico 00931, United States
| | - Timothy B. Parks
- VA Caribbean Healthcare System, 10 Casia Street, San Juan, Puerto Rico 00921, United States
| | - Charlene Munet-Colón
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, Río Piedras, Puerto Rico 00931, United States
| | - Arthur D. Tinoco
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, Río Piedras, Puerto Rico 00931, United States
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Loza-Rosas SA, Saxena M, Delgado Y, Gaur K, Pandrala M, Tinoco AD. A ubiquitous metal, difficult to track: towards an understanding of the regulation of titanium(iv) in humans. Metallomics 2017; 9:346-356. [PMID: 28164202 PMCID: PMC5397357 DOI: 10.1039/c6mt00223d] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Despite the ubiquitous nature of titanium(iv) and several examples of its beneficial behavior in different organisms, the metal remains underappreciated in biology. There is little understanding of how the metal might play an important function in the human body. Nonetheless, a new insight is obtained regarding the molecular mechanisms that regulate the blood speciation of the metal to maintain it in a nontoxic and potentially bioavailable form for use in the body. This review surveys the literature on Ti(iv) application in prosthetics and in the development of anticancer therapeutics to gain an insight into soluble Ti(iv) influx in the body and its long-term impact. The limitation in analytical tools makes it difficult to depict the full picture of how Ti(iv) is transported and distributed throughout the body. An improved understanding of Ti function and its interaction with biomolecules will be helpful in developing future technologies for its imaging in the body.
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Affiliation(s)
- Sergio A Loza-Rosas
- Department of Chemistry, University of Puerto Rico, Rio Piedras, San Juan, PR 00969, USA.
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Florès O, Trommenschlager A, Amor S, Marques F, Silva F, Gano L, Denat F, Cabral Campello MP, Goze C, Bodio E, Le Gendre P. In vitro and in vivo trackable titanocene-based complexes using optical imaging or SPECT. Dalton Trans 2017; 46:14548-14555. [DOI: 10.1039/c7dt01981e] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Two unprecedented titanocene-based theranostics have been synthesized, characterized, and tracked either in vitro (BODIPY probe) or in vivo (111In-DOTA probe).
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de la Cueva-Alique I, Muñoz-Moreno L, Benabdelouahab Y, Elie BT, El Amrani MA, Mosquera MEG, Contel M, Bajo AM, Cuenca T, Royo E. Novel enantiopure cyclopentadienyl Ti(IV) oximato compounds as potential anticancer agents. J Inorg Biochem 2016; 156:22-34. [PMID: 26717259 PMCID: PMC4882921 DOI: 10.1016/j.jinorgbio.2015.12.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 12/02/2015] [Accepted: 12/08/2015] [Indexed: 11/28/2022]
Abstract
The synthesis and characterization of new enantiopure cyclopentadienyl titanium oximato compounds (S,R)-[(η(5)-C5H5)Ti{к(2)NO,(R)NH·HCl}Cl2] (R=Ph (phenyl) 1a·HCl, Bn (benzyl) 1b·HCl, 2-pic (2-picolyl) 1c·HCl), (S,R)-[(η(5)-C5H5)TiCl2{к(2)NO,(Ph)NH}] (1a) and (S,R)-[(η(5)-C5H5)2TiCl{к(2)NO,(R)NH}] (R=Ph 2a, Bn 2b, 2-pic 2c), along with studies on their behavior in D2O at different pD values are reported. The structure of previously described ammonium-oxime (2S,5R)-{NOH,(Bn)NH·HCl} (b·HCl) and novel titanium derivative 1a have been determined by single crystal X-ray crystallography. The effect of the compounds on cytotoxicity, cell adhesion and migration of the androgen-independent prostate cancer PC-3 cells has been assessed. Compounds 2b and 2c are more cytotoxic than additive doses of titanocene dichloride and free oxime proligand, probing the synergistic effect of these novel compounds. The cytotoxicity of 2b and 2c has been further evaluated against human renal Caki-1, colon DLD-1 and triple negative breast MDA-MB-231 cancer cell lines. The activity found for 2c on PC-3 and Caki-1 is higher than that of highly active Titanocene Y (bis-[(p-methoxybenzyl)cyclopentadienyl]titanium(IV) dichloride), while showing selectivity against renal cancer when compared to a non-tumorigenic human renal (HEK-293T) cell line. Compounds 2b and especially 2c are apoptotic in Caki-1 cancer cell lines. Cell adhesion and wound-healing assays confirmed that derivatives 1c·HCl, 2b and 2c affect the adhesion and migration patterns of the PC-3 cell line. Interactions of the novel compounds with plasmid (pBR322) DNA have also been studied, showing that the oximato Ti(IV) derivatives have a weak or no interaction with DNA at physiological pH.
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Affiliation(s)
- Isabel de la Cueva-Alique
- Departamento de Química Orgánica y Química Inorgánica, Facultad de Biología, Ciencias Ambientales y Química, Universidad de Alcalá, 28871 Alcalá de Henares, Madrid, Spain
| | - Laura Muñoz-Moreno
- Departamento de Biología de Sistemas, Facultad de Biología, Ciencias Ambientales y Química, Universidad de Alcalá, 28871 Alcalá de Henares, Madrid, Spain
| | - Yosra Benabdelouahab
- Departamento de Química Orgánica y Química Inorgánica, Facultad de Biología, Ciencias Ambientales y Química, Universidad de Alcalá, 28871 Alcalá de Henares, Madrid, Spain
| | - Benelita T Elie
- Department of Chemistry, Brooklyn College, The City University of New York, Brooklyn, New York, NY 11210, USA; Chemistry and Biology PhD Programs, The Graduate Center, The City University of New York, 365 Fifth Avenue, New York, NY, 10016, USA
| | - Mohammed Amin El Amrani
- Université Abdelmalek Essaadi, Departement de Chemie-Laboratoire de Chimie Organique Appliquée, Mhannech II, B.P. 2121, Tétouan, Morocco
| | - Marta E G Mosquera
- Departamento de Química Orgánica y Química Inorgánica, Facultad de Biología, Ciencias Ambientales y Química, Universidad de Alcalá, 28871 Alcalá de Henares, Madrid, Spain
| | - María Contel
- Department of Chemistry, Brooklyn College, The City University of New York, Brooklyn, New York, NY 11210, USA; Chemistry and Biology PhD Programs, The Graduate Center, The City University of New York, 365 Fifth Avenue, New York, NY, 10016, USA
| | - Ana M Bajo
- Departamento de Biología de Sistemas, Facultad de Biología, Ciencias Ambientales y Química, Universidad de Alcalá, 28871 Alcalá de Henares, Madrid, Spain
| | - Tomás Cuenca
- Departamento de Química Orgánica y Química Inorgánica, Facultad de Biología, Ciencias Ambientales y Química, Universidad de Alcalá, 28871 Alcalá de Henares, Madrid, Spain
| | - Eva Royo
- Departamento de Química Orgánica y Química Inorgánica, Facultad de Biología, Ciencias Ambientales y Química, Universidad de Alcalá, 28871 Alcalá de Henares, Madrid, Spain.
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Pinkas J, Lamač M. Transformations of functional groups attached to cyclopentadienyl or related ligands in group 4 metal complexes. Coord Chem Rev 2015. [DOI: 10.1016/j.ccr.2015.03.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Heng MP, Sinniah SK, Teoh WY, Sim KS, Ng SW, Cheah YK, Tan KW. Synthesis of a DNA-targeting nickel (II) complex with testosterone thiosemicarbazone which exhibits selective cytotoxicity towards human prostate cancer cells (LNCaP). SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2015; 150:360-372. [PMID: 26057090 DOI: 10.1016/j.saa.2015.05.095] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 05/27/2015] [Accepted: 05/28/2015] [Indexed: 06/04/2023]
Abstract
Testosterone thiosemicarbazone, L and its nickel (II) complex 1 were synthesized and characterized by using FTIR, CHN, (1)H NMR, and X-ray crystallography. X-ray diffraction study confirmed the formation of L from condensation of testosterone and thiosemicarbazide. Mononuclear complex 1 is coordinated to two Schiff base ligands via two imine nitrogens and two tautomeric thiol sulfurs. The cytotoxicity of both compounds was investigated via MTT assay with cisplatin as positive reference standard. L is more potent towards androgen-dependent LNCaP (prostate) and HCT 116 (colon). On the other hand, complex 1, which is in a distorted square planar environment with L acting as a bidentate NS-donor ligand, is capable of inhibiting the growth of all the cancer cell lines tested, including PC-3 (prostate). It is noteworthy that both compounds are less toxic towards human colon cell CCD-18Co. The intrinsic DNA binding constant (Kb) of both compounds were evaluated via UV-Vis spectrophotometry. Both compounds showed Kb values which are comparable to the reported Kb value of typical classical intercalator such as ethidium bromide. The binding constant of the complex is almost double compared with ligand L. Both compounds were unable to inhibit the action topoisomerase I, which is the common target in cancer treatment (especially colon cancer). This suggest a topoisomerase I independent-cell death mechanism.
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Affiliation(s)
- Mok Piew Heng
- Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia; Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 Serdang, Malaysia
| | - Saravana Kumar Sinniah
- Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
| | - Wuen Yew Teoh
- Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
| | - Kae Shin Sim
- Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
| | - Seik Weng Ng
- Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia; Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah, Saudi Arabia
| | - Yoke Kqueen Cheah
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 Serdang, Malaysia
| | - Kong Wai Tan
- Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
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Synthesis of substituted titanocene dichloride derivatives by hydrosilylation. J Organomet Chem 2014. [DOI: 10.1016/j.jorganchem.2014.06.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Gansäuer A, Okkel A, Schwach L, Wagner L, Selig A, Prokop A. Triazol-substituted titanocenes by strain-driven 1,3-dipolar cycloadditions. Beilstein J Org Chem 2014; 10:1630-7. [PMID: 25161720 PMCID: PMC4142980 DOI: 10.3762/bjoc.10.169] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Accepted: 06/27/2014] [Indexed: 11/23/2022] Open
Abstract
An operationally simple, convenient, and mild strategy for the synthesis of triazole-substituted titanocenes via strain-driven 1,3-dipolar cycloadditions between azide-functionalized titanocenes and cyclooctyne has been developed. It features the first synthesis of titanocenes containing azide groups. These compounds constitute ‘second-generation’ functionalized titanocene building blocks for further synthetic elaboration. Our synthesis is modular and large numbers of the complexes can in principle be prepared in short periods of time. Some of the triazole-substituted titanocenes display high cyctotoxic activity against BJAB cells. Comparison of the most active complexes allows the identification of structural features essential for biological activity.
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Affiliation(s)
- Andreas Gansäuer
- Kekulé-Institut für Organische Chemie und Biochemie der Rheinischen Friedrich-Wilhelms-Universität Bonn, Gerhard-Domagk-Straße 1, D-53121 Bonn, Germany
| | - Andreas Okkel
- Kekulé-Institut für Organische Chemie und Biochemie der Rheinischen Friedrich-Wilhelms-Universität Bonn, Gerhard-Domagk-Straße 1, D-53121 Bonn, Germany
| | - Lukas Schwach
- Kekulé-Institut für Organische Chemie und Biochemie der Rheinischen Friedrich-Wilhelms-Universität Bonn, Gerhard-Domagk-Straße 1, D-53121 Bonn, Germany
| | - Laura Wagner
- Medizinische Klinik für Hämatologie, Onkologie und Tumorimmunologie Campus Vichow Klinikum Charité Berlin, Augustenburger Platz 1, D-13353 Berlin, Germany
| | - Anja Selig
- Medizinische Klinik für Hämatologie, Onkologie und Tumorimmunologie Campus Vichow Klinikum Charité Berlin, Augustenburger Platz 1, D-13353 Berlin, Germany
| | - Aram Prokop
- Abteilung für Kinderonkologie /-hämatologie Kinderkrankenhaus der Stadt Köln Amsterdamerstrasse 59, D-50735 Köln, Germany
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Bansal R, Acharya PC. Man-Made Cytotoxic Steroids: Exemplary Agents for Cancer Therapy. Chem Rev 2014; 114:6986-7005. [DOI: 10.1021/cr4002935] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Ranju Bansal
- University Institute of Pharmaceutical
Sciences, Panjab University, Chandigarh-160014, India
| | - Pratap Chandra Acharya
- University Institute of Pharmaceutical
Sciences, Panjab University, Chandigarh-160014, India
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Ceballos-Torres J, Virag P, Cenariu M, Prashar S, Fajardo M, Fischer-Fodor E, Gómez-Ruiz S. Anti-cancer applications of titanocene-functionalised nanostructured systems: an insight into cell death mechanisms. Chemistry 2014; 20:10811-28. [PMID: 24715574 DOI: 10.1002/chem.201400300] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Indexed: 12/20/2022]
Abstract
A series of alkenyl-substituted titanocene compounds have been supported on the mesoporous silica-based material KIT-6. The corresponding functionalised materials were completely characterised by different techniques (solid-state multinuclear NMR spectroscopy, IR spectroscopy, N2 adsorption-desorption isotherms, X-ray fluorescence and diffraction, SEM and TEM) to observe the incorporation of the titanocene derivatives on the external surface of the material KIT-6. Both the titanocene compounds and the materials were tested in vitro against a wide variety of human cancer and normal cell lines. A very high cytotoxicity of the synthesised titanocene derivatives (IC50 values in the range of those described in the literature for the most active cytotoxic titanocene compounds), with selectivity towards cancer cell lines was observed. The cytotoxic activity of the materials is the highest reported to date for titanocene-functionalised materials. In addition, higher Ti uptake (from 4 to 23% of the initial amount of Ti) of the cells treated with materials was observed with respect to those treated with "free" titanocene derivatives (which gave Ti uptake values from 0.4 to 4.6% of the initial amount of Ti). Additional experiments with the titanocene derivatives and the functionalised materials revealed that changes to the morphological and functional dynamics of apoptosis occurred when the active titanocene species were incorporated into mesoporous materials. In addition, the materials could induce programmed cell death in tumour cell populations by impairing the damaged DNA repair mechanisms and by upregulation of intrinsic and extrinsic apoptotic signalling pathways.
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Affiliation(s)
- Jesús Ceballos-Torres
- Departamento de Química Inorgánica y Analítica, E.S.C.E.T. Universidad Rey Juan Carlos, 28933 Móstoles, Madrid (Spain)
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Ramos G, Loperena Y, Ortiz G, Reyes F, Szeto A, Vera J, Velez J, Morales J, Morrero D, Castillo L, Dharmawardhane S, Melendez E, Washington AV. The addition of a pregnenolone pendant group enhances the anticancer properties of titanocene dichloride in a mcf-7 xenograft model. Anticancer Res 2014; 34:1609-1615. [PMID: 24692689 PMCID: PMC4053690] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
BACKGROUND/AIM Titanocene dichloride held great promise as a chemotherapeutic compound in pre-clinical studies. However, subsequent clinical trials revealed hepatoxicity and nephrotoxicity, which limited its use in clinical applications. Therefore, we used steroid pendant groups to improve the targeting of titanocene in MCF-7 breast cancer cells, and demonstrated a 10-fold lower effective dose compared to titanocene in in vitro assays. The aim of the present study was to test the efficacy of a titanocene functionalized with pregnenolone (Ti-Preg) in an in vivo breast cancer model. MATERIALS AND METHODS Xenografts from the MCF7 breast cancer cell line were implanted into athymic nu/nu mice to evaluate the potential of Ti-Preg as an anti-breast cancer agent. RESULTS Ti-Preg demonstrated significant inhibition of MCF-7 tumor growth when compared to vehicle and to titanocene controls. CONCLUSION Our findings demonstrate the potential of steroid pendent groups for targeting chemotherapeutics to steroid hormone-dependent cancer.
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Affiliation(s)
- Gladiany Ramos
- Department of Biology, University of Puerto Rico - Reciento Rio Piedras, PO Box 23360, San Juan, Puerto Rico 00931.
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Mijatović S, Bulatović M, Mojić M, Stošić-Grujičić S, Miljković D, Maksimović-Ivanić D, Gómez-Ruiz S, Pinkas J, Horáček M, Kaluđerović GN. Study of the anticancer properties of methyl- and phenyl-substituted carbon- and silicon-bridged ansa-titanocene complexes. J Organomet Chem 2014. [DOI: 10.1016/j.jorganchem.2013.07.059] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Affiliation(s)
- Franck Le Bideau
- Institut de Chimie de Strasbourg (UMR 7177), CNRS-Université de Strasbourg , Strasbourg 67000, France
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Cini M, Bradshaw TD, Lewis W, Woodward S. Cuprate Addition to a 6-Substituted Pentafulvene - Preparation ofsec-Alkyl-Substituted Titanocene Dichlorides and Their Biological Activity. European J Org Chem 2013. [DOI: 10.1002/ejoc.201300474] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Gómez-Ruiz S, Maksimović-Ivanić D, Mijatović S, Kaluđerović GN. On the discovery, biological effects, and use of Cisplatin and metallocenes in anticancer chemotherapy. Bioinorg Chem Appl 2012; 2012:140284. [PMID: 22844263 PMCID: PMC3401524 DOI: 10.1155/2012/140284] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2012] [Accepted: 05/19/2012] [Indexed: 01/08/2023] Open
Abstract
The purpose of this paper is to summarize mode of action of cisplatin on the tumor cells, a brief outlook on the metallocene compounds as antitumor drugs as well as the future tendencies for the use of the latter in anticancer chemotherapy. Molecular mechanisms of cisplatin interaction with DNA, DNA repair mechanisms, and cellular proteins are discussed. Molecular background of the sensitivity and resistance to cisplatin, as well as its influence on the efficacy of the antitumor immune response was evaluated. Furthermore, herein are summarized some metallocenes (titanocene, vanadocene, molybdocene, ferrocene, and zirconocene) with high antitumor activity.
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Affiliation(s)
- Santiago Gómez-Ruiz
- Departamento de Química Inorgánica y Analítica, E.S.C.E.T., Universidad Rey Juan Carlos, 28933 Móstoles, Spain
| | - Danijela Maksimović-Ivanić
- Institute for Biological Research “Sinisa Stankovic”, University of Belgrade, Boulevard of Despot Stefan 142, 11060 Belgrade, Serbia
| | - Sanja Mijatović
- Institute for Biological Research “Sinisa Stankovic”, University of Belgrade, Boulevard of Despot Stefan 142, 11060 Belgrade, Serbia
| | - Goran N. Kaluđerović
- Institut für Chemie, Martin-Luther-Universität Halle-Wittenberg, Kurt-Mothes-Straße 2, 06120 Halle, Germany
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Abstract
The application use of organometallic compounds into the cancer research was established in the late 1970s by Köpf-Maeir and Köpf. This new research area has been developed for the past thirty years. In the early 1980s, Jaouen and coworkers recognized the potential application of organometallic compounds vectorized with pendant groups that can deliver the drug to certain specific receptors. This is what is called nowdays Target Specific Drugs. This review will focus on metallocenes vectorized with steroids derivatives of hormones, nonsteroidal and selective endrocrine modulator.
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Affiliation(s)
- Enrique Meléndez
- University of Puerto Rico, Department of Chemistry, PO Box 9019 Mayagüez, PR 00681
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Synthesis and biological evaluation of achiral indole-substituted titanocene dichloride derivatives. INTERNATIONAL JOURNAL OF MEDICINAL CHEMISTRY 2012; 2012:905981. [PMID: 25954531 PMCID: PMC4412094 DOI: 10.1155/2012/905981] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Revised: 03/15/2012] [Accepted: 03/15/2012] [Indexed: 11/17/2022]
Abstract
Six new titanocene compounds have been isolated and characterised. These compounds were synthesised from their fulvene precursors using Super Hydride (LiBEt3H) followed by transmetallation with titanium tetrachloride to yield the corresponding titanocene dichloride derivatives. These complexes are bis-[((1-methyl-3-diethylaminomethyl)indol-2-yl)methylcyclopentadienyl] titanium (IV) dichloride (5a), bis-[((5-methoxy-1-methyl,3-diethylaminomethyl)indol-2-yl)methylcyclopentadienyl] titanium (IV) dichloride (5b), bis-[((1-methyl,3-diethylaminomethyl)indol-4-yl)methylcyclopentadienyl] titanium (IV) dichloride (5c), bis-[((5-bromo-1-methyl)indol-3-yl)methylcyclopentadienyl] titanium (IV) dichloride (5d), bis-[((5-chloro-1-methyl)indol-3-yl)methylcyclopentadienyl] titanium (IV) dichloride (5e), and bis-[((5-fluoro-1-methyl)indol-3-yl)methylcyclopentadienyl] titanium (IV) dichloride (5f). All six titanocenes 5a–5f were tested for their cytotoxicity through MTT-based in vitro tests on CAKI-1 cell lines using DMSO and Soluphor P as solubilising agents in order to determine their IC50 values. Titanocenes 5a–5f were found to have IC50 values of 10 (±2), 21 (±3), 29 (±4), 140 (±6), and 450 (±10) μM when tested using DMSO.
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Ceballos-Torres J, Gómez-Ruiz S, Kaluđerović GN, Fajardo M, Paschke R, Prashar S. Naphthyl-substituted titanocene dichloride complexes: Synthesis, characterization and in vitro studies. J Organomet Chem 2012. [DOI: 10.1016/j.jorganchem.2011.12.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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Affiliation(s)
- Katherine M. Buettner
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Ann M. Valentine
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States
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González-Pantoja JF, Stern M, Jarzecki AA, Royo E, Robles-Escajeda E, Varela-Ramírez A, Aguilera RJ, Contel M. Titanocene-phosphine derivatives as precursors to cytotoxic heterometallic TiAu2 and TiM (M = Pd, Pt) compounds. Studies of their interactions with DNA. Inorg Chem 2011; 50:11099-110. [PMID: 21958150 PMCID: PMC3205237 DOI: 10.1021/ic201647h] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
A series of tri- and bimetallic titanium-gold, titanium-palladium, and titanium-platinum derivatives of the general formulas [Ti{η(5)-C(5)H(4)(CH(2))(n)PPh(2)(AuCl)}(2)]·2THF [n = 0 (1); n = 2 (2); n = 3 (3)] and [TiCl(2){η(5)-C(5)H(4)κ-(CH(2))(n)PPh(2)}(2)(MCl(2))]·2THF [M = Pd, n = 0 (4); n = 2 (5); n = 3 (6) ; M = Pt, n = 0 (7); n = 2 (8); n = 3 (9)] have been synthesized and characterized by different spectroscopic techniques and mass spectrometry. The molecular structures of compounds 1-9 have been investigated by means of density functional theory calculations. The calculated IR spectra of the optimized structures fit well with the experimental IR data obtained for 1-9. The stability of the heterometallic compounds in deuterated solvents [CDCl(3), dimethyl sulfoxide (DMSO)-d(6), and mixtures 50:50 DMSO-d(6)/D(2)O and 1:99 DMSO-d(6)/D(2)O at acidic and neutral pH] has been evaluated by (31)P and (1)H NMR spectroscopy showing a higher stability for these compounds than for Cp(2)TiCl(2) or precursors [Ti{η(5)-C(5)H(4)(CH(2))(n)PPh(2)}(2)]. The new compounds display a lower acidity (1-2 units) than Cp(2)TiCl(2). The decomposition products have been identified over time. Complexes 1-9 have been tested as potential anticancer agents, and their cytotoxicity properties were evaluated in vitro against HeLa human cervical carcinoma and DU-145 human prostate cancer cells. TiAu(2) and TiPd compounds were highly cytotoxic for these two cell lines. The interactions of the compounds with calf thymus DNA have been evaluated by thermal denaturation (1-9) and by circular dichroism (1, 3, 4, and 7) spectroscopic methods. All of these complexes show a stronger interaction with DNA than that displayed by Cp(2)TiCl(2) at neutral pH. The data are consistent with electrostatic interactions with DNA for TiAu(2) compounds and for a covalent binding mode for TiM (M = Pd, Pt) complexes.
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Affiliation(s)
- Jose F. González-Pantoja
- Department of Chemistry, Brooklyn College and The Graduate Center, The City University of New York, Brooklyn, NY, 11210, US
| | - Michael Stern
- Department of Chemistry, Brooklyn College and The Graduate Center, The City University of New York, Brooklyn, NY, 11210, US
| | - Andrzej A. Jarzecki
- Department of Chemistry, Brooklyn College and The Graduate Center, The City University of New York, Brooklyn, NY, 11210, US
| | - Eva Royo
- Departamento de Química Inorgánica, Facultad de Ciencias, Universidad de Alcalá, 28871 Alcalá de Henares, Madrid, Spain
| | - Elisa Robles-Escajeda
- Department of Biological Sciences, The University of Texas at El Paso, El Paso, TX 79968, US
| | - Armando Varela-Ramírez
- Department of Biological Sciences, The University of Texas at El Paso, El Paso, TX 79968, US
| | - Renato J. Aguilera
- Department of Biological Sciences, The University of Texas at El Paso, El Paso, TX 79968, US
| | - María Contel
- Department of Chemistry, Brooklyn College and The Graduate Center, The City University of New York, Brooklyn, NY, 11210, US
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Morales A, Santana A, Althoff G, Melendez E. Host-Guest Interactions between Calixarenes and Cp(2)NbCl(2). J Organomet Chem 2011; 696:2519-2527. [PMID: 21709809 PMCID: PMC3119540 DOI: 10.1016/j.jorganchem.2011.03.021] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The possible inclusion complexes of Cp(2)NbCl(2) into calixarenes hosts have been investigated. The existence of a true inclusion complex in the solid state was confirmed by a combination of NMR, ab-initio calculations, thermogravimetric analysis, FTIR, Raman and PXRD. Ab-initio calculations, (1)H NMR solution and solid state (13)C CP MAS NMR results demonstrated that p-sulfonic calix[6]arene does form an inclusion complex with Cp(2)NbCl(2). Raman spectroscopy showed, for the inclusion compound of p-sulfonic calix[6]arene-Cp(2)NbCl(2), a band between 500-850 cm(-1) characteristic of Nb-O vibration. This result suggests that Nb(V) may engage in coordination with the oxygen of the sulfonate group, as part of the host-guest interaction. However, it is important to mention that the niobocene dichloride (Cp(2)NbCl(2)) dissolves in water and undergoes oxidation and hydrolysis processes to yield Cp(2)NbCl(2)(OH) species. For that reason this band does not exclude that the Nb-O band belongs to Cp(2)NbCl(2)(OH). Solid State (13)C CP MAS NMR and solution (1)H NMR spectroscopies together with ab-initio results showed that Cp(2)NbCl(2) is included in the p-sulfonic calix[6]arene cavity, with both Cp rings inside the cavity. In contrast, the solution (1)H NMR results demonstrated that calix[6]arene does not form inclusion complex with Cp(2)NbCl(2) in CDCl(3) solution. Cp(2)NbCl(2) is not included in the calix[6]arene cavity, possibly due to the lack of sulfonate heads which promote Nb-O interactions and assist the inclusion of Cp(2)NbCl(2) into the cavity.
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Affiliation(s)
- Alexis Morales
- Department of Chemistry, University of Puerto Rico, Mayagüez, PR 00681
| | - Alberto Santana
- Department of Chemistry, University of Puerto Rico, Mayagüez, PR 00681
| | - Gerhard Althoff
- Bruker BioSpin GmbH, Silberstreifen, 76287 Rheinstetten Germany
| | - Enrique Melendez
- Department of Chemistry, University of Puerto Rico, Mayagüez, PR 00681
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