Design,synthesis, and antibacterial studies of potent pyrazolinyltriazoles

Research on Chemical Intermediates - A library of pyrazolinyltriazole hybrids (3a–l, 4a–l) was synthesized via azide–alkyne dipolar (Huisgen) cycloaddition of azidoacetyl...     

Fluoro-substituted ketones from nitriles using acidic and basic reaction conditions

Fluoro-substituted aliphatic nitriles are shown to undergo the Houben-Hoesch reactions with arenes in CF₃SO₃H to give fluoro-substituted ketones in good yields. The fluorine substituents appear to enhance the reactivities of the nitriles (and the nitrilium ion intermediates) compared to similar aliphatic nitriles. Fluoro-substituted ketones are also shown to be accessible through the reactions of organometallic reagents and fluoro-substituted nitriles.     

Medium-ring aminocyclitols: a concise synthesis of nine-membered aminocarbasugar analogs and the solid-state supramolecular architectures of two key precursors

A stereocontrolled synthesis of nine-membered aminocarbasugar analogs (amino-cyclononanoses) from a rigid bicyclo[4.3.1]deca-2,4-dien-10-one platform, harboring a latent functionalized cyclononane ring, is described.     

Bacteriocin release protein-mediated secretory expression of recombinant chalcone synthase in Escherichia coli

Flavonoids are secondary metabolites synthesized by plants shown to exhibit health benefits such as anti-inflammatory, antioxidant, and anti-tumor effects. Thus, due to the importance of this compound, several enzymes involved in the flavonoid pathway have been cloned and characterized in Escherichia coli. However, the formation of inclusion bodies has become a major disadvantage of this approach. As an alternative, chalcone synthase from Physcomitrella patens was secreted into the medium using a bacteriocin release protein expression vector. Secretion of P. patens chalcone synthase into the culture media was achieved by co-expression with a psW1 plasmid encoding bacteriocin release protein in E. coli Tuner (DE3) plysS. The optimized conditions, which include the incubation of cells for 20 h with 40 ng/ml mitomycin C at OD₆₀₀ induction time of 0.5 was found to be the best condition for chalcone synthase secretion.     

Reductive Alkylation Causes the Formation of a Molten Globule-Like Intermediate Structure in <Emphasis Type="Italic">Geobacillus zalihae</Emphasis> Strain T1 Thermostable Lipase

A thermostable lipase from Geobacillus zalihae strain T1 was chemically modified using propionaldehyde via reductive alkylation. The targeted alkylation sites were lysines, in which T1 lipase possessed 11 residues. Far-UV circular dichroism (CD) spectra of both native and alkylated enzyme showed a similar broad minimum between 208 and 222 nm, thus suggesting a substantial amount of secondary structures in modified enzyme, as compared with the corresponding native enzyme. The hydrolytic activity of the modified enzymes dropped drastically by nearly 15-fold upon chemical modification, despite both the native and modified form showed distinctive α-helical bands at 208 and 222 nm in CD spectra, leading us to the hypothesis of formation of a molten globule (MG)-like structure. As cooperative unfolding transitions were observed, the modified lipase was distinguished from the native state, in which the former possessed a denaturation temperature (T _m) in lower temperature range at 61 °C while the latter at 68 °C. This was further supported by 8-anilino-1-naphthalenesulfonic acid (ANS) probed fluorescence which indicated higher exposure of hydrophobic residues, consequential of chemical modification. Based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis, a small number of lysine residues were confirmed to be alkylated.     

Regulation of photosynthesis, fluorescence, stomatal conductance and water-use efficiency of cowpea (Vigna unguiculata [L.] Walp.) under drought

Drought is the major abiotic stress factor that causes extensive losses to agriculture production worldwide. The objective of this study was to evaluate the dynamics of photosynthesis and water-use efficiency parameters in 15 cowpea genotypes under well-watered and drought condition. Photosynthesis (A) and chlorophyll fluorescence (Fv'/Fm') declined linearly with decreasing soil water content whereas intrinsic water-use efficiency (WUE) increased under drought stress, suggesting stomatal regulation was a major limitation to photosynthesis. However, under increasing drought conditions, increase in ratio of intercellular CO(2) to ambient CO(2) concentrations along with reduced WUE showed the role of non-stomatal limitation of photosynthesis. The resistant nature of Fv'/Fm' and electron transport rate under drought appeared to be important mechanisms for photoinhibition protection under drought stress. Oxidative stress was apparent due to drought-induced reduction in total chlorophyll and carotenoid which was accompanied with increased leaf wax contents. The accumulation of proline appeared to be in response of drought injury rather than a drought tolerance mechanism. A clear separation based on the genotypes site of origin among the genotypes for drought tolerance could not be established when analyzed using principal component analysis. The identified genotypes and physiological traits from this study may be useful for genetic engineering and breeding programs integrating drought adaptation in cowpea.     

N-heterocyclic carbene-catalyzed 1,3-dipolar cycloaddition reactions: a facile synthesis of 3,5-di- and 3,4,5-trisubstituted isoxazoles

A first example of organo-N-heterocyclic carbene (NHC) catalyzed click-type fast 1,3-dipolar cycloaddition of nitrile oxides with alkynes was developed for the regioselective synthesis of 3,5-di- and 3,4,5-trisubstituted isoxazoles. Triethylamine (Et(3)N) was employed as an effective base to generate both nitrile oxide and the organo-NHC catalyst in situ. This catalytic approach was used to attach a variety of substituents, including other biologically active fragments, onto the isoxazole ring to selectively design multinucleus structures. Further, we have also optimized the conditions for Cu(I)-free Sonogashira cross-coupling to obtain internal alkynes in high yields, which were subsequently used in cycloaddition. A catalytic cycle is proposed and the remarkable regiocontrol in the formation of isoxazoles was ascribed to a beneficial zwitterion intermediate developed by the interaction of the strongly nucleophilic organo-NHC catalyst with alkyne followed by nitrile oxide.     

Effect of terminal N-substitution in 2-oxo-1,2-dihydroquinoline-3-carbaldehyde thiosemicarbazones on the mode of coordination, structure, interaction with protein, radical scavenging and cytotoxic activity of copper(II) complexes

Four 2-oxo-1,2-dihydroquinoline-3-carbaldehyde N-substituted thiosemicarbazone ligands (H(2)-OQtsc-R, where R = H, Me, Et or Ph) and their corresponding new copper(II) complexes [CuCl(2)(H(2)-OQtsc-H)]·2H(2)O (1), [CuCl(2)(H(2)-OQtsc-Me)]·2H(2)O (2), [CuCl(2)(H(2)-OQtsc-Et)(CH(3)OH)]Cl (3) and [CuCl(H-OQtsc-Ph)]·CH(3)OH (4) have been synthesized in order to correlate the effect of terminal N-substitution on coordination behaviour, structure and biological activity. Single crystal X-ray diffraction studies revealed that the complexes 1, 2 and 3 have square pyramidal geometry around the central metal ion. In the complexes 1 and 2, the copper ion is coordinated by the ligand with ONS donor atoms, one chloride ion in apical position and the other chloride in the basal plane. Complex 3 consists of [CuCl(2)(H(2)-OQtsc-Et)(CH(3)OH)](+) cation and a chloride as counter ion. The copper ion is coordinated by the ligand with ONS donor atoms and by one chloride ion in the basal plane. One methanol molecule is bonded through its neutral oxygen in the apical position. Complex 4 is square planar with the ligand coordinating through uni-negative tridentate ONS(-) and by one chloride ion in the basal plane. The binding of complexes with lysozyme protein was carried out by fluorescence spectroscopy. Investigations of antioxidation properties showed that all the copper(II) complexes have strong radical scavenging properties. The cytotoxicity of the complexes 3 and 4 against NIH 3T3 and HeLa cell lines showed that synergy between the metal and ligands results in a significant enhancement in the cell death with IC(50) of ~10-40 μM. A size dependence of substitution at terminal N in the thiosemicarbazones on the biological activities of the complexes has been observed.     

Linear or cross-shaped di(cyclopentadienyltitanium) compounds with aryl or heteroaryl spacers

The preparation of hexamethylated and hexabenzylated arylene or heteroarylene bridged dinuclear di(cyclopentadienyltitanium) compounds from the reaction of the corresponding hexachlorides with methyllithium or benzylmagnesium chloride is described. The spacers between the cyclopentadienyl rings consist of one, two or three phenylene groups, a dioctyloxyphenylene group or a 2,2'-bithienylene group. The corresponding hexachlorides and hexaisopropoxides have also been prepared.     

Nephroprotective and antioxidant activities of Salacia oblonga on acetaminophen-induced toxicity in rats

Salacia oblonga, a woody climbing plant belonging to the family Celastaceae, is widely distributed in India and other southeast Asian countries. The genus Salacia have been used particularly for the treatment of diabetes, obesity, gonorrhoea, rheumatism, pruritus and asthma. Acetaminophen (APAP), used as an analgesic drug, produces liver and kidney necrosis in mammals at high doses. The aim of this study was to investigate the nephroprotective and antioxidant activities of the ethanol extract of Salacia oblonga (EESO) at the two dose levels of 250 and 500 mg/kg?bw on APAP-induced toxicity in rats. The results showed that APAP significantly increases the levels of serum urea, creatinine, and reduces levels of uric acid concentration. The EESO reduces these by increasing anti-oxidative responses as assessed by biochemical and histopathological parameters. In conclusion, our results suggest that the EESO possesses nephroprotective and antioxidant effects against APAP-induced nephrotoxicity in rats.