Ish Kumar

Bismuth(III) complexes derived from non-steroidal anti-inflammatory drugs and their activity against Helicobacter pylori.

The formation of bismuth(III) complexes of carboxylates and benzoates derived from the 1 : 3 reaction of BiPh(3) with the common non-steroidal anti-inflammatory drugs (NSAIDs) ketoprofen, naproxen, ibuprofen, mefenamic acid, diflunisal, 5-chlorosalicylic acid, fenbufen, sulindac, tolfenamic acid and flufenamic acid, has been achieved using both solvent-free and solvent-mediated methods. The thermochemical profiles of the solvent-free reactions were studied using DSC-TGA. All reactions produced the tris-substituted complexes of general formula [BiL(3)](n), with the complexes derived from ketoprofen and sulindac having an additional single bismuth bound H(2)O molecule in the inner coordination sphere. The complexes are stable in air over a period of six months, do not undergo significant decomposition when suspended overnight in water, but decompose in 1 M HCl solution to release the free acid form of the NSAID. All ten complexes show excellent in vitro activity against Helicobacter pylori with MIC values of > or = 6.25 microg mL(-1).

Bismuth(III) 5-sulfosalicylate complexes: structure, solubility and activity against Helicobacter pylori

Treatment of 5-sulfosalicylic acid (H(3)Ssal) with BiPh(3) results in the formation of the first dianionic carboxylate-sulfonate bismuth complex, [PhBi(HSsal)H(2)O](infinity) 1a, and its ethanol analogue [PhBi(HSsal)EtOH](infinity) 1b (space group P2(1)/c), while Bi(OAc)(3) gives the mixed monoanionic and dianionic complex, {[Bi(HSsal)(H(2)Ssal)(H(2)O)(3)](2) x 2 H(2)O}(infinity) 2 (space group P1). The three complexes are all polymeric in the solid state as determined by single crystal X-ray diffraction, with extended frameworks constructed from dimeric [Bi(HSsal)](2), 1a and 1b, or from [Bi(HSsal)(H(2)Ssal)](2) units, 2. The heteroleptic bismuth complexes 1a and 2 display remarkable aqueous solubility, 10 and 2.5 mg ml(-1) respectively, resulting in a clear solution of pH 1.5. In contrast, 1b is essentially insoluble in aqueous environments. All three complexes show significant activity against the bacterium Helicobacter pylori of <6.25 microg ml(-1).

Structural and solution studies of phenylbismuth(III) sulfonate complexes and their activity against Helicobacter pylori

Three bis-phenylbismuth sulfonates [Ph(2)Bi(O(3)SR)](∞) (R = p-tolyl 1, mesityl 2 or S-(+)-10-camphoryl 3) have been synthesised and characterised. Their tendency for ligand redistribution in solution, and activity against the bacterium Helicobacter pylori have been investigated. The structures of 2 and 3 have been authenticated by X-ray diffraction crystallography. They are structurally very similar with polymeric helical chain structures composed of four coordinate Bi atoms which bridge between two sulfonate O atoms with near linear O-Bi-O bond angles. The two phenyl rings are cis to one another and trans to the stereochemically active lone pair. Upon dissolution of the pure compounds 1, 2 and 3, a ligand redistribution reaction occurs in which the mono-phenylbismuth bis-sulfonates, the bismuth tris-sulfonates and triphenylbismuth are formed. Two further complexes of general formula [PhBi(O(3)SR)(2)](∞) (where R = p-tolyl 4, and mesityl 5) were thus obtained and their crystal structures determined. The presence of the single sulfonato ligand in compounds 1, 2 and 3 resulted in a dramatic increase in bacteriocidial activity towards H. pylori (MIC values of ≥6.25 μg mL(-1)) relative to BiPh(3) (>64 μg mL(-1)) and the sulfonic acids, which were essentially inactive.

Making Bispirin: synthesis, structure and activity against Helicobacter pylori of bismuth(III) acetylsalicylate

Reaction of Bi(O(t)Bu)3 with aspirin (acetylsalicylic acid = aspH) in dry toluene results in the bismuth(III) complex, [Bi(O2C(C6H4)OAc)3]∞ 1 (O2C(C6H4)OAc = asp), minimum inhibitory concentration (MIC) against Helicobacter pylori ≥ 6.25 μg mL(-1), while the inclusion of a stoichiometric equivalent of KO(t)Bu leads to crystals of the bismuthate salt [KBi(O2C(C6H4)OAc)4]∞ 2.

Synthetic and structural comparisons of bismuth(III) carboxylates synthesised under solvent-free and reflux conditions.

Two synthetic approaches to the formation of bismuth(III) carboxylates have been explored and compared. Ph(3)Bi was reacted with a series of carboxylic acids (RCO(2)H) of varying pK(a) and functionality (R = PhCH[double bond, length as m-dash]CH, o-MeOC(6)H(4), m-MeOC(6)H(4), o-H(2)NC(6)H, o-O(2)NC(6)H(4), p-O(2)NC(6)H(4), 2-(C(5)H(4)N)) under reflux conditions in toluene and solvent-free. The thermochemical profiles of the solvent-free reactions were also studied by DSC-TGA. All reactions produced the tri-substituted bismuth carboxylates in comparable yields and purity with the exceptions of picolinic acid and p-nitrobenzoic acid. 2-Picolinic acid exclusively formed the di-substituted complex, [PhBi(2-(C(5)H(4)N)CO(2))(2)](4), by both methods, while p-nitrobenzoic acid gave the tri-substituted complex through reflux and the di-substituted complex under solvent-free conditions. Two of the complexes were structurally authenticated by single crystal X-ray diffraction: [PhBi(2-(C(5)H(4)N)CO(2))(2)](4) is tetrameric formed through five membered chelate rings involving the pyridyl N and O(-C) rather than the less stable carboxylate (-CO(2)) chelates, while [Bi(o-MeOC(6)H(4)CO(2))(3)](infinity), is a polymer in which dimeric units, constructed around two chelating and one unsymmetrical bridging carboxylate on each Bi centre, are then joined together through longer intermolecular Bi-O bridging bonds.

High-Performance Hybrid Bismuth-Carbon Nanotube Based Contrast Agent for X-ray CT Imaging

Carbon nanotubes (CNTs) have been used for a plethora of biomedical applications, including their use as delivery vehicles for drugs, imaging agents, proteins, DNA, and other materials. Here, we describe the synthesis and characterization of a new CNT-based contrast agent (CA) for X-ray computed tomography (CT) imaging. The CA is a hybrid material derived from ultrashort single-walled carbon nanotubes (20-80 nm long, US-tubes) and Bi(III) oxo-salicylate clusters with four Bi(III) ions per cluster (Bi4C). The element bismuth was chosen over iodine, which is the conventional element used for CT CAs in the clinic today due to its high X-ray attenuation capability and its low toxicity, which makes bismuth a more-promising element for new CT CA design. The new CA contains 20% by weight bismuth with no detectable release of bismuth after a 48 h challenge by various biological media at 37 °C, demonstrating the presence of a strong interaction between the two components of the hybrid material. The performance of the new Bi4C@US-tubes solid material as a CT CA has been assessed using a clinical scanner and found to possess an X-ray attenuation ability of >2000 Hounsfield units (HU).

Cytoplasmic-Nuclear Male Sterility: Origin, Evaluation and Utilization

Cytoplasmic-nuclear male sterility (CMS), a potential system for economical hybrid seeds production, results from disharmonious interaction between the cytoplasmic and nuclear genetic factors. Evaluation of CMS system for its utility is determined by many factors. Unstable male sterility increases cost and affects quality of hybrid seed production. Cooler weather during panicle development promotes instability in maize and pigeonpea, high humidity in pearl millet and hot temperature of 42°C and above in sorghum. Effect of genetic background of B-lines on male sterility has been found in case of A1 CMS system in pearl millet and sorghum, and fertility restorer gene expressivity in rice. Maintainer gene frequency in germplasm is another factor to be considered which has bearing on genetic diversification of A-lines. In case of A1 CMS system in sorghum and pearl millet landraces have greater proportion as restorers. Character association influences the commercial viability of a CMS system. Approaches to estimate the diversity of CMS systems to enhance the exploitation of outstanding inbred lines and also to overcome the risk of disease and pest epidemics, include both traditional field evaluation of hybrids for differential patterns of male fertility restoration and RFLP analysis of mitochondrial DNA. Steps involved in CMS utilization in hybrid cultivar breeding including (i) identification of potential CMS sources, (ii) development of seed parents (A lines) exhibiting complete sterility, (iii) maintenance of seed parents by taking appropriate steps to prevent contamination with foreign pollen, (iv) development of restorer parents through identification of promising restorers, genetic improvement of existing restorers and transfer of restorer genes into high yielding inbred lines and (v) hybrid seed production keeping in view the four key elements — isolation distance, off type removal, flowering synchrony between A- and R-lines, and A:R lines ratio are discussed.