Sensing and formation of a stable gel in the presence of picric acid by a low-molecular-weight-gelator

In this work, a set of amide-based compounds, L1-L3, have been studied. These compounds are decorated with various H-bonding functional groups while the presence of aromatic rings not only promote π?π stacking but also made these molecules electron-rich. All three compounds were utilized for the sensing of electron-deficient nitro-explosives. These compounds were found to be highly selective for the nanomolar sensing of picric acid (PA). Out of three compounds, L3 acted as a low-molecular-weight-gelator and formed a more stable and stronger gel in the presence of PA. The resultant [email protected]L3?gel was studied by the SEM, powder XRD and rheological techniques while further supported by the molecular docking studies. These results illustrate that doping of L3 with PA not only enhances several noteworthy interaction avenues but also the stability of the resultant [email protected]L3?gel when compared to L3?gel.     

Cellulosic biomass biocomposites with polyaniline,polypyrrole and sodium alginate: Insecticide adsorption-desorption,equilibrium and kinetics studies

This work was designed to synthesize and characterize biocomposites for the adsorptive elimination of insecticide (nitenpyram). Different biocomposites were synthesized of polyaniline (PAN-PH), polypyrrole (PPY-PH) and sodium alginate (Na-Al-PH) with cellulosic biomass of peanut husk (PH), which was characterized fourier-transform infrared spectroscopy (FTIR), pH_pzc and scanning electron microscope (SEM). In batch mode, different variables, i.e., contact time, pH, temperature, NP (nitenpyram) concentration and adsorbent dose effects were investigated. The adsorption capacities of PH, PAN-PH, PPY-PH and Na-Al-PH were recorded to be 13.0, 14.43, 13.61 and 11.91 (mg/g), respectively at 30 °C, 60 min contact time, 0.05 g and 2.0 pH. Pseudo second order kinetic and Freundlich isotherm models best explained the NP adsorption data. An exothermic adsorption nature of NP adsorption was observed on to PH, PAN-PH, PPY-PH and Na-Al-PH. The NP desorption was efficient with NaOH and biocomposites are competent for the adsorptive removal of NP, which can utilized for NP remediation in effluents.     

Synthesis, spectroscopic and thermal studies of transition metal complexes derived from benzil and diethylenetriamine

A macrocyclic ligand, bdta (where bdta=3,6,9,12,15,18-hexaaza-1,2,10,11-tetraphenyl-2,9,11,18-tetraenecyclododecane) has been prepared by cyclocondensation of benzil with diethylenetriamine which efficiently encapsulates transition as well as pseudo-transition metal ions leading to the formation of M(bdta)Cl2 type complexes [where M=Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II)]. The analytical, spectroscopic and magnetic moment data suggests an octahedral geometry for all the complexes. EPR spectra of Mn(II) and Cu(II) show considerable exchange interaction in the complex. They are non-conducting in DMSO. The TGA profile of the ligand and its complexes are identical and consists of two discreet stages. The voltammogram of Cu-complex exhibits a quasi-reversible one-electron transfer wave for Cu(II)/Cu(I) couple.     

Isolation of quercetin and mandelic acid from <Emphasis Type="Italic">Aesculus indica</Emphasis> fruit and their biological activities

Background

In this study Aesculus indica fruit was subjected to isolation of phytochemicals. Two antioxidants quercetin and Mandelic acid were isolated in pure state. The free radical scavenging and acetyl choline esterase inhibitory potential of the crude extract and sub fractions were also determined.

Results

The antioxidant capacity of crude extract, fractions and isolated compounds were determined by DPPH and ABTS methods. Folin-Ciocalteu reagent method was used to estimate the total phenolic contents and were found to be 78.34?±?0.96, 44.16?±?1.05, 65.45?±?1.29, 37.85?±?1.44 and 50.23?±?2.431 (mg/g of gallic acid) in crude extract, ethyl acetate, chloroform, n-hexane and aqueous fractions respectively. The flavonoid concentration in crude extract, ethyl acetate, chloroform, n-hexane and aqueous fraction were; 85.30?±?1.20, 53.80?±?1.07, 77.50?±?1.12, 26.30?±?1.35 and 37.78?±?1.25 (mg/g of quercetin) respectively. The chloroform fraction was more potent against enzymes, acetyl choline esterase and butyryl choline esterase (IC₅₀?=?85 and 160 μg/ml respectively). The phenolic compounds in the crude extract and fractions were determined using HPLC standard method. Chlorogenic acid, quercetin, phloroglucinol, rutin, mandelic acid and hydroxy benzoic acid were detected at retention times 6.005, 10.062, 22.623, 30.597, 35.490 and 36.211 in crude extract and different fractions. The ethyl acetate fraction was rich in the targeted compounds and was therefore subjected to column isolation. The HPLC chromatogram of isolated compounds showed single peak at specified retention times which confirms their isolation in pure state. The isolated compounds were then characterized by FTIR and NMR spectrophotometric techniques.

Conclusion

The Aesculus indica fruit extracts showed antioxidant and anticholine esterase inhibitory potentials. Two bioactive compounds were isolated in the pure form ethyl acetate fraction. From results it was concluded that the fruit of this plant could be used to minimize oxidative stress caused by reactive oxygen species.

     

Synthesis of 3,4,5-substituted furan-2(5<Emphasis Type="Italic">H</Emphasis>)-ones using Al-doped ZnO nanostructure

Al-doped ZnO nanostructures were prepared via a simple precipitation method and were characterized by several techniques including XRD, TEM, EDX, UV–Vis, and DLS. All XRD patterns show the hexagonal single-phase structure of pure and Al-doped ZnO nanopowders without impurity. The samples consist of particles with average sizes ranging from 53 to 60 nm measured by DLS technique. Next, the catalytic activity of pure and Al-doped ZnO nanopowders was investigated in terms of synthesis of 3,4,5-substituted furan-2(5H)-one derivatives using the three-component reaction of aldehydes, aromatic amines, and acetylenic esters. This procedure has advantages such as high yields, simple methodology, and easy work-up.     

Voltammetric Behavior of 1,4‐Dimethoxypillar[m]arene[n]quinones

The electrochemical properties of a series of 1,4‐dimethoxypillar[m]arene[n]quinones (DMP[m]A[n]Qs) and the interactions between individual quinone units have been investigated on glassy carbon electrode in acetonitrile. All the quinone units showed relative electron uptake behavior except 1,4‐dimethoxypillar[5]quinones (DMP[5]Q). The results have shown that the electrochemical behavior of the DMP[m]A[n]Qs is comparatively different from that of their related linear quinone analogues. The resultant properties were attributed to the close proximity of redox‐active sites as well as the delocalization of electrons on the aromatic rings. Another aspect to be considered responsible for their electronic properties was suggested to be the electrostatic repulsions between adjacent quinone units in these complex structures. Current studies provide a better understanding on the voltammetric behavior of pillararene derivatives with different numbers of quinone units as well as their future scope in certain future electrochemical applications.     

Base-Promoted One-Pot Synthesis of Pyridine Derivatives via Aromatic Alkyne Annulation Using Benzamides as Nitrogen Source

In the presence of Cs₂CO₃, the first simple, efficient, and one-pot procedure for the synthesis of 3,5-diaryl pyridines via a variety of aromatic terminal alkynes with benzamides as the nitrogen source in sulfolane is described. The formation of pyridine derivatives accompanies the outcome of 1,3-diaryl propenes, which are also useful intermediates in organic synthesis. Thus, pyridine ring results from a formal [2+2+1+1] cyclocondensation of three alkynes with benzamides, and one of the alkynes provides one carbon, whilst benzamides provide a nitrogen source only. A new transformation of alkynes as well as new utility of benzamide are found in this work.     

Antioxidant activity of some lichen metabolites

Antioxidant activity of several classes of lichen metabolites were assessed in the in vitro superoxide radical (SOR), nitric oxide radical and 2,2-diphenyl-1-picrylhydrazil radical scavenging assays. The despsides sekikaic acid and lecanoric acid showed promising antioxidant activity in SOR assay with IC?? values of 82.0?±?0.3?μmol and 91.5?±?2.1?μmol, respectively, while the depsidone lobaric acid exhibited an IC?? value of 97.9?±?1.6?μmol, all relative to the standard, propyl gallate (IC???=?106.0?±?1.7?μmol). One of the most abundant mononuclear phenolic compounds, methyl-β-orcinol carboxylate was found to be a potent NO scavenger (IC???=?84.7?± 0.1?μmol), compared to the standard rutin (IC???=?86.8?±?1.9?μmol).     

Surface‐Enhanced Fluorescence from Fluorophore‐Assembled Monolayers by Using Ag@SiO2 Nanoparticles

A new and simple procedure to enhance the fluorescence of analytes on the surfaces of a solid substrate is demonstrated based on Ag@SiO₂ nanoparticles. Two kinds of silver–silica core–shell nanoparticles with shell thicknesses of around 3 and 15 nm have been prepared and used as enhancing agents, respectively. By simply pipetting drops of the enhancing agents onto substrate surfaces with Rose Bengal monolayers, an enhancement of about 27 times, compared with the control sample, is achieved by using the Ag@SiO₂ nanoparticles with shells of about 3 nm, whereas an enhancement of around 11.7 times is obtained when using those with thicker shells. The effects of shell thickness and surface density of the enhancing agents on the enhancement have been investigated experimentally. The results show that this method can be potentially helpful in fluorescence‐based surface analysis.