Biodegradation and bioaccumulation of fenitrothion in rat liver

The biodegradation of fenitrothion O,O-dimethyl-O-(3-methyl-4-nitro phenyl) phosphorothioate was investigated in rat liver after administration of various doses (5 mg/100 g body weight and 20 mg/100 g body weight) in acute treatment and 1 mg/100 g body weight in chronic treatment. High performance liquid chromatography of the pesticide and its metabolites formed in liver in acute treatment showed time-dependent sequential conversion of pesticide into three major metabolites within 24 h. These metabolites were separated and purified to homogenity by HPLC and characterized by IR spectroscopy as O,O-dimethyl-O-(3-methyl-4-amino phenyl) phsophorothioate (metabolite 1), O,O-dimethyl phosphorothioate (metabolite II) and O,O-dimethyl phosphate (metabolite III) in the fi rst dose (5 mg/100 g body weight). Metabolite II was found to be different in the second dose (20 mg/100 g body weight) and identified as O,O-dimethyl O-3-methyl-4-amino phenyl phosphate. The results with the fi rst dose indicated reduction of the nitro group in fenitrothion as step I followed by hydrolytic clevage of the P-O-aryl bond in metabolite I and oxidative desulphurylation of metabolite II. At higher dose (20 mg/100 g body weight) oxidative desulphurylation takes place as step II followed by hydrolysis of metabolite II. The bioaccumulation of fenitrothion within 60 days during chronic treatment showed no metabolite but continuous reduction in fenitrothion concentration, indicating excretion of pesticide and its products in urine and in faeces.     

Pyrocatechol Violet immobilized Amberlite XAD-2: synthesis and metal-ion uptake properties suitable for analytical applications

Amberlite XAD-2 has been functionalized by coupling it, through the ---N=N--- group, with Pyrocatechol Violet (PV), and the resulting resin has been characterized by elemental analysis, thermogravimetric analysis (TGA) and IR spectra. The resin has been used for preconcentrating Zn(II), Cd(II), Pb(II) and Ni(II) ions prior to their determination by flame atomic absorption spectrometry. The optimum pH values for quantitative sorption are 5, 5–7, 4, and 3 for Zn, Cd, Pb and Ni, respectively. The four metals can be desorbed (recovery ˜98%) with 4 M HNO₃; also, 4 M HCl is equally suitable except for Zn. The sorption capacity of the resin is 1410, 1270, 620 and 1360 μg g⁻¹ resin for Zn, Cd, Ni and Pb, respectively. The effect of F⁻, Cl⁻, NO₃⁻, SO₄²⁻ and PO₄³⁻ on the sorption of these four metal ions has been investigated. They are tolerable in the range 0.01–0.20 M, for Pb. In the sorption of Zn(II) and Ni(II), the tolerance limits of all these ions are upto 0.01 M, whereas for Cd(II), F⁻, NO₃⁻, and PO₄³⁻ have been found to be tolerable upto 0.50, 0.10 and 0.10 M, respectively. The preconcentration factors are 60, 50, 23 and 18 for Zn, Cd, Pb and Ni, respectively. Simultaneous collection and determination of the four metals are possible. Cations commonly present in drinking water do not affect the sorption of either metal ion if present at a concentration level similar to that of water. The method has been applied to determine Zn, Ni and Pb content of well-water samples (RSD ≤9%).     

“Click-switch” – one-step conversion of organic azides into photochromic diarylethenes for the generation of light-controlled systems

Diarylethenes (DAEs) are an established class of photochromic molecules, but their effective incorporation into pre-existing targets is synthetically difficult. Here we describe a new class of DAEs in which one of the aryl rings is a 1,2,3-triazole that is formed by “click” chemistry between an azide on the target and a matching alkyne–cyclopentene–thiophene component. This late-stage zero-length linking allows for tight integration of the DAE with the target, thereby increasing the chances for photomodulation of target functions. Nineteen different DAEs were synthesized and their properties investigated. All showed photochromism. Electron-withdrawing groups, and in particular −M-substituents at the triazole and/or thiophene moiety resulted in DAEs with high photo- and thermostability. Further, the chemical nature of the cyclopentene bridge had a strong influence on the behaviour upon UV light irradiation. Incorporation of perfluorinated cyclopentene led to compounds with high photo- and thermostability, but the reversible photochromic reaction was restricted to halogenated solvents. Compounds containing the perhydrogenated cyclopentene bridge, on the other hand, allowed the reversible photochromic reaction in a wide range of solvents, but had on average lower photo- and thermostabilities. The combination of the perhydrocyclopentene bridge and electron-withdrawing groups resulted in a DAE with improved photostability and no solvent restriction. Quantum chemical calculations helped to identify the photoproducts formed in halogenated as well as non-halogenated solvents. For two optimized DAE photoswitches, photostationary state composition and reaction quantum yields were determined. These data revealed efficient photochemical ring closure and opening. We envision applications of these new photochromic diarylethenes in photonics, nanotechnology, photobiology, photopharmacology and materials science.

New photochromic diarylethenes are reported in which one aryl ring is a 1,2,3-triazole that is formed by “click” chemistry between an azide on the target and a matching alkyne–cyclopentene–thiophene component.     

Free-energy landscape of alcohol driven coacervation transition in aqueous gelatin solutions

Liquid-liquid phase separation of a homogeneous polyampholyte (gelatin) solution into a dense polymer-rich coacervate and the dilute supernatant phase is discussed through free-energy landscape formalism. We have evaluated the free energy and entropy of the system as it undergoes the phenomenon of simple coacervation, driven by the addition of a nonsolvent. Electrophoretic mobility (mu) and turbidity measurements were performed on 0.01% and 0.05% (w/v) aqueous gelatin solutions that were driven towards coacervation by the addition of ethanol. The mobility of the polyampholyte molecules, which was typically mu approximately 0.38+/-0.02 microm/s cm/V in water, gradually reduced for the soluble intermolecular complexes to a plateau value of mu approximately 0.11+/-0.01 microm/s cm/V as the ethanol volume fraction equaled phi(ns) approximately 0.47+/-0.03, which coincided with the first appearance of coacervate droplets (coacervation transition) observed from turbidity measurements, a behavior found to be invariant of gelatin concentration. These results were used as input to the theoretical model to explicitly construct the free-energy landscape for a single gelatin chain and the global system comprising the polymer-rich coacervate and the dilute supernatant phase.     

Synthesis and antibacterial evaluation of nitrogen containing novel heterocyclic chalcones

Thirteen different novel heterocyclic chalcones were synthesized using cycloaddition and Claisen–Schmidt condensation reactions. These newly synthesized compounds were characterized by their spectral studies and structure of (E)-3-(4-methoxyphenyl)-1-(5-methyl-1-(pyridin-3-yl)-1H-1,2,3-triazol-4-yl)prop-2-en-1-one (4h) was also evidenced by single crystal X-ray studies. These compounds were evaluated for antibacterial activities against seven bacterial strains in vitro. Compounds 4b and 4c containing 4-fluoro and 4-chloro groups have shown remarkable inhibition as showed by the standard drug ciprofloxacin against Escherichia coli and Staphylococcus aureus, respectively. Another compound 4k containing 3,4,5-trimethoxy group also showed similar activity against both these strains. Beside these three potential compounds 4b, 4c, 4k, one more compound 4g containing 4-methyl group showed equivalent inhibition as that of standard drug against E. coli. These categories of compounds are therefore good candidates for developing new effective antibacterial in future.     

Saccharonol B,a new cytotoxic methylated isocoumarin from Saccharomonospora azurea

From an antimicrobial gram-positive actinomycete strain of Saccharomonospora azurea (MTCC11714) isolated from high altitude soil of Kargil (J&K, India), a new isocoumarin saccharonol B (2) along with two known compounds viz. saccharonol A (1) and piericidin A₃ (3) was isolated and characterized. The structure of the new compound was established based on extensive 2D-NMR data. Saccharonol B (2) exhibited mild antimicrobial activity against a standard panel of microorganisms Staphylococcus aureus ATCC 29213, Candida albicans ATCC 90028, and Aspergillus fumigatus MTCC 1811 with MIC values in the range of 128–248 μg/mL. Saccharonol B (2) and piericidin A₃ (3) showed selective cytotoxic activity against human pancreatic carcinoma cell line (MIAPaCa-2) with IC₅₀ values of 9 and 8 μM, respectively. Mechanistic studies indicated that saccharonol B (2) arrests S-phase of the cell cycle and causes dose-dependent loss of mitochondrial potential in MIAPaCa-2 cells.     

Structure – Directing Effect of Renewable Resource Based Amphiphilic Dopants on the Formation of Conducting Polyaniline-Clay Nanocomposite

Summary: The structure-directing effect of two amphiphilic dopants on the nucleation and growth mechanism during the formation of micro/ nanostructured polyaniline (PANI) and polyaniline-clay nanocomposites (PANICNs) is described. PANIs and PANICNs were prepared by in-situ intercalative emulsion polymerization of aniline using the amphiphilic dopants, 3-pentadecyl phenyl phosphoric acid (3-PDPPA) and 3-pentadecyl phenol–4-sulphonic acid (3-PDPSA), derived from cashew nut shell liquid, a renewable resource. These molecules act as intercalating agents, dopants and also as structure-directing agents. X- ray diffraction (XRD) and scanning electron microscopic (SEM) studies revealed the formation of lamellar/fibrillar – network in PANI- PDPPA and cylinder/rod morphology in PANI-PDPSA. Experimental data reveal that fibrillar morphology arises from the heterogeneous nucleation followed by an indefinite growth mechanism. On the other hand rod-like structures are formed from the self-assembled rod-like micelle guided polymerization through homonucleation followed by an anisotropic growth mechanism. Electrical conductivity measurement revealed lower conductivities for PANICNs than that of PANIs.