In vitro DNA binding, pBR322 cleavage and molecular docking studies of 1,2-diaminobenzene, dichloro glycyl glycinate tin(IV) and zirconium(IV) complexes

De novo design and synthesis of complexes 1,2-diaminobenzene, dichloro glycyl glycinate tin(IV) and zirconium(IV), 1 and 2 as molecular drug entities were carried out. The structure elucidation of 1 and 2 was done by analytical techniques and spectroscopic methods viz. IR, UV-vis, ¹H, ¹³C, ¹¹⁹Sn NMR, ESI-Mass and XRD techniques. In vitro DNA binding studies of 1 and 2 by various biophysical techniques viz electronic absorption, emission spectroscopy and circular dichroism measurements were carried out to evaluate their potential to act as chemotherapeutic candidates; furthermore, cleavage studies with pBR322plasmid DNA and computer-aided molecular docking studies were also done to study the mechanistic pathway and mode of binding at the molecular level. The observed results revealed that complex 1 exhibited greater DNA binding propensity in contrast to complex 2 primarily via electrostatic binding mode. The pBR322 DNA cleavage studies of both the complexes revealed the hydrolytic cleavage mechanism and DNA minor groove binding, which was ascertained by molecular docking studies of the drug candidate. Communicated by Ramaswamy H. Sarma.

Monophosphoramide derivatives: synthesis and crystal structure, theoretical and experimental studies of their biological effects

Synthesizing new chemical compounds and studying their biological applications have been important issues in scientific research. In this investigation, we synthesized and characterized ten new N-acetyl phosphoramidate compounds and explored the crystal structure of three others. Furthermore, not only were some kinetic inhibition parameters measured, like IC₅₀, K_i, k_p, K_D for 7 compounds on human acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), but also their hydrophobic parameter was determined by shake-flask technique. All compounds (number 1-10) were investigated for anti-bacterial activity against three Gram-positive and three Gram-negative bacteria, while chloramphenicol was used as a standard antibiotic. In order to find new insecticide, toxicities of 13 acephate (Ace)-derived compounds (number 20-32) were bioassayed on third larval instar of elm leaf beetle and Xanthogaleruca luteola. Additionally, screening in vivo tests revealed that two compounds had had the greatest insecticidal potential in comparison with others. It means these ones inhibited AChE (with mixed mechanisms) and general esterase more than the rest. According to ChE-QSAR models, the inhibitory potency for enzyme and bacteria is directly influenced by the electronic parameters versus structural descriptors. AChE-QSPR model of fluorescence assay indicated that the inhibitory power of AChE is primarily influenced by a set of electronic factors with the priority of: E_HB > PL > δ(³¹P) versus structural descriptor (SA and Mv). Synthesizing new chemical compounds and studying their biological applications have been important issues in scientific research. Toxicities of 13 acephate (Ace)-derived compounds (number 20-32) were bioassayed on third larval instar of elm leaf beetle and Xanthogaleruca luteola. Insect-QSAR equations of these compounds, based on MLR and PCA, showed that non-descriptor net charge nitrogen atom (which was affected by the polarization of N-H group) had the greatest effect on insecticidal potential.

Enhancing the Activity of Drugs by Conjugation to Organometallic Fragments

Resistance to chemotherapy is a current clinical problem, especially in the treatment of microbial infections and cancer. One strategy to overcome this is to make new derivatives of existing drugs by conjugation to organometallic fragments, either by an appropriate linker, or by direct coordination of the drug to a metal. We illustrate this with examples of conjugated organometallic metallocene sandwich and half-sandwich complexes, RuII and OsII arene, and RhIII and IrIII cyclopentadienyl half-sandwich complexes. Ferrocene conjugates are particularly promising. The ferrocene-chloroquine conjugate ferroquine is in clinical trials for malaria treatment, and a ferrocene-tamoxifen derivative (a ferrocifen) seems likely to enter anticancer trails soon. Several other examples illustrate that organometallic conjugation can restore the activity of drugs to which resistance has developed.

The elements of life and medicines

Which elements are essential for human life? Here we make an element-by-element journey through the periodic table and attempt to assess whether elements are essential or not, and if they are, whether there is a relevant code for them in the human genome. There are many difficulties such as the human biochemistry of several so-called essential elements is not well understood, and it is not clear how we should classify elements that are involved in the destruction of invading microorganisms, or elements which are essential for microorganisms with which we live in symbiosis. In general, genes do not code for the elements themselves, but for specific chemical species, i.e. for the element, its oxidation state, type and number of coordinated ligands, and the coordination geometry. Today, the biological periodic table is in a position somewhat similar to Mendeleev's chemical periodic table of 1869: there are gaps and we need to do more research to fill them. The periodic table also offers potential for novel therapeutic and diagnostic agents, based on not only essential elements, but also non-essential elements, and on radionuclides. Although the potential for inorganic chemistry in medicine was realized more than 2000 years ago, this area of research is still in its infancy. Future advances in the design of inorganic drugs require more knowledge of their mechanism of action, including target sites and metabolism. Temporal speciation of elements in their biological environments at the atomic level is a major challenge, for which new methods are urgently needed.

Potentially bioactive organotin(IV) compounds: synthesis, characterization, in vitro bioactivities and interaction with SS-DNA

Fourteen new organotin(IV) complexes with general formula R2SnL2 or R3SnL where R = CH3, C2H5, C4H9, C6H5, C6H11, CH2-C6H5, C(CH3)3, C8H17 and L = N-[(2-methoxyphenyl)]-4-oxo-4-[oxy]butanamide were synthesized and characterized by elemental analyses, FT-IR, NMR ((1)H, (13)C and (119)Sn), mass spectrometry and single crystal X-ray structural analysis. Crystallographic data for four triorganotin(IV) complexes (R3SnL, R = CH3, C2H5, C4H9, CH2-C6H5) showed the tin has approximate trigonal bipyramidal geometry with the R groups in the trigonal plane. The carboxylate groups of ligands L bridge adjacent tin atoms, resulting in polymeric chains. In case of the diorganotin(IV) derivatives a six-coordinate geometry at the tin atom is proposed from spectroscopic evidence. The Me-Sn-Me bond angle in complex 7 was determined from the (2)J[(119)Sn-(1)H] value as 166.3° that falls in the range of six-coordinate geometry. The ligand and its complexes (1-14) were screened for their antimicrobial, antitumor, cytotoxic and antileishmanial activities and found to be biologically active. The ligand and its complexes bind to DNA via intercalative interactions resulting in hypochromism and minor bathochromic shifts as confirmed by UV-visible spectroscopy. Based on in vitro studies such as the potato disc method, the synthesized compounds were found to possess significant antitumor activity. Also, from cytotoxicity and DNA interaction studies, these compounds can also be used for the prevention and treatment of cancer. Gel electrophoresis assay was used to investigate the damage to double stranded super coiled plasmid pBR322 DNA by the synthesized compounds and compounds 1 and 7 were found to cause the maximum damage. All the synthesized compounds exhibit strong antileishmanial activity that was even higher than that of Amphotericin B, with significant cytotoxicity. This study, therefore, demonstrated the potential use of these compounds as source of novel agents for the treatment of leishmaniasis.

ATR-FTIR spectroscopy detects alterations induced by organotin(IV) carboxylates in MCF-7 cells at sub-cytotoxic/-genotoxic concentrations

The environmental impact of metal complexes such as organotin(IV) compounds is of increasing concern. Genotoxic effects of organotin(IV) compounds (0.01 mug/ml, 0.1 mug/ml or 1.0 mug/ml) were measured using the alkaline single-cell gel electrophoresis (comet) assay to measure DNA single-strand breaks (SSBs) and the cytokinesis-block micronucleus (CBMN) assay to determine micronucleus formation. Biochemical-cell signatures were also ascertained using attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy. In the comet assay, organotin(IV) carboxylates induced significantly-elevated levels of DNA SSBs. Elevated micronucleus-forming activities were also observed. Following interrogation using ATR-FTIR spectroscopy, infrared spectra in the biomolecular range (900 cm-1 - 1800 cm-1) derived from organotin-treated MCF-7 cells exhibited clear alterations in their biochemical-cell fingerprint compared to control-cell populations following exposures as low as 0.0001 mug/ml. Mono-, di- or tri-organotin(IV) carboxylates (0.1 mug/ml, 1.0 mug/ml or 10.0 mug/ml) were markedly cytotoxic as determined by the clonogenic assay following treatment of MCF-7 cells with >/= 1.0 mug/ml. Our results demonstrate that ATR-FTIR spectroscopy can be applied to detect molecular alterations induced by organotin(IV) compounds at sub-cytotoxic and sub-genotoxic concentrations. This biophysical approach points to a novel means of assessing risk associated with environmental contaminants.PACS codes: 87.15.-v, 87.17.-d, 87.18.-h.

Synthesis, crystal structures, cytotoxicity and qualitative structure-activity relationship (QSAR) of cis-bis{5-[(E)-2-(aryl)-1-diazenyl]quinolinolato}di-n-butyltin(IV) complexes, (n)Bu2Sn(L)2

A series of cis-bis{5-[(E)-2-(aryl)-1-diazenyl]quinolinolato}di-n-butyltin(IV) complexes has been synthesized and characterized by (1)H-, (13)C-, (119)Sn NMR, ESI-MS (electrospray ionization mass spectrometry), IR and (119m)Sn Mössbauer spectroscopic techniques in combination with elemental analyses. The structures of four di-n-butyltin(IV) complexes, viz., (n)Bu(2)Sn(L(3))(2) (3), (n)Bu(2)Sn(L(4))(2) (4), (n)Bu(2)Sn(L(5))(2) (5) and (n)Bu(2)Sn(L(7))(2).0.5C(6)H(6) (7) (LH=5-[(E)-2-(aryl)-1-diazenyl)quinolin-8-ol) were determined by single crystal X-ray diffraction. In general, the complexes were found to adopt a distorted cis-octahedral arrangement around the tin atom. These complexes retain their solid-state structure in non-coordinating solvent as evidenced by (119)Sn and (13)C NMR spectroscopic results. The in vitro cytotoxicity of di-n-butyltin(IV) complexes (3-8) is reported against seven well characterized human tumour cell lines. The basicity of the two quinolinolato donor N and O atoms of the ligands are discussed in relation to the cytotoxicity data.