Suberitane sesterterpenoids from the Antarctic sponge Phorbas areolatus (Thiele, 1905)

Following ecological and chemical screenings, the Antarctic sponge Phorbas areolatus was chemically investigated for the first time. Three new suberitane derivatives named isosuberitenone B, 19-episuberitenone B, and isoxaspirosuberitenone were identified together with the known compounds suberitenones A and B, and oxaspirosuberitenone after a thorough inspection of their NMR data. These compounds were found to exhibit moderate cytotoxic activity and their presence in this sponge rules out their use as a chemotaxonomic marker for Suberites sponges.     

An efficient 1,2-chelation-controlled reduction of protected hydroxy ketones via Red-Al

In this paper, we have demonstrated that Red-Al is an efficient chelation-controlled reducing reagent for acyclic acetal (i.e., MOM, MEM, SEM, and BOM) protected alpha-hydroxy ketones. Typically, diastereomeric ratios (dr) ranged from 5 to 20:1 for the 1,2- anti-diols in good to excellent yields.     

Quantitative determination of macroelement and microelement content of fresh and processed bamboo shoots by wavelength dispersive X-ray fluorescence spectrometry

Bamboo shoots are considered as healthy and nutritional food as they supply proteins, dietary fiber, phenols, phytosterols, vitamins, and minerals in considerable quantities and capture a novel place in the spectrum of plant foods. Besides nutrients and bioactive compounds, shoots also contain antinutrient (cyanogen) that needs to be removed by adequate processing prior to consumption. This study was undertaken to investigate the effects of fermentation, brine preservation, and boiling on levels of mineral elements in shoots of Dendrocalamus hamiltonii using wavelength dispersive X-ray fluorescence (WD-XRF) spectrometry. WD-XRF spectrometry is a method that causes the least destruction to the raw plant material as no harsh chemicals are used and gives the most accurate results. Fermentation process resulted in significant increase in the levels of Rb (9%), S (11%), Mg (12%), Zn (46%), Ca (56%), and Fe (87%); however, Na (18.79 g/100 g, dry weight), Cl (24.73 g/100 g, dry weight), and Br (20.0 mg/100 g, dry weight) content increased drastically after brine preservation. Boiling increased the levels of Fe by 139% but did not affect the Rb (20.0 mg/100 g, dry weight) and Zn content (10.2 mg/100 g, dry weight) of the shoots. In general, fermentation, which led to the lowest loss of mineral elements, appears the best method in enhancement and retention of the mineral content in bamboo shoots and holds the prospect at industrial and society levels.     

Effect of proton irradiation on electrical properties of a-As2S3

This paper reports the effect of proton irradiation on the electrical properties of a-As₂S₃ in the temperature range of 323–418 K and frequency range 0.1–100 kHz. The variation of transport property is studied with proton irradiation dose (1 × 10¹³ ions/cm² and 1 × 10¹⁵ ions/cm²). It has been observed that proton irradiation changes the dc conductivity (σ_dc), dc activation energy (ΔE_dc) and ac conductivity (σ_ac(ω)). The σ_dc and σ_ac(ω) increases with dose of proton irradiation. The value of frequency exponent (s) decreases with the temperature and irradiation dose. These results are explained in terms of change in density of defect states in these glasses.     

Investigations on regio‐ and stereoselectivities in cycloadditions involving α‐ (3‐pyridyl)‐N‐phenylnitrone: Development of an efficient route to novel nicotine analogs

Thermal reactions of hitherto α‐(3‐pyridyl)‐N‐phenylnitrone ( 1 ) with mono‐substituted electron‐rich and electron‐neutral dipolarophiles are regio‐, and stereo‐selective (exo‐selective), controlled by LUMO ‐ dipole ‐ HOMO‐ dipolarophile interaction, and furnish syn‐5‐substituted‐3‐(3‐pyridyl)‐isoxazolidines ( 5 ) in high yields. With electron deficient dipolarophiles such as acrylonitrile there is observed a loss of regioselectivity as well as stereoselectivity and the regioselectivity is reversed in reactions with methyl vinyl ketone and methyl acrylate, due to intervention of HOMO‐dipole ‐ LUMO‐dipolarophile interaction, affording 4‐substi‐tuted‐3‐(3‐pyridyl)‐isoxazolidines ( 7 ) as major products. Reactions of nitrone ( 1 ) with disubstituted dipolarophiles such as methyl methacrylate and ethyl coronate furnish methyl syn‐5‐methy‐3‐pyridyl‐1‐phenyl‐isoxazolidine‐5‐carboxylate ( 8 ) and ethyl anti‐5‐methy‐3‐pyridyl‐1‐phenyl‐isoxazolidine‐4‐carboxylate ( 10 ), respectively, in high yields. Reaction with N‐Phenylmaleimide affords novel isoxazolidino‐pyrro‐lidinediones bearing a 3‐pyridyl moiety ( 11, 12 ). A mechanistic rationalization of the obtained results in terms of electronic, steric and secondary interactions is proffered.     

Unusual aggregates from the oxidation of alkene self-assembled monolayers: a previously unrecognized mechanism for SAM ozonolysis?

Self-assembled monolayers (SAMs) of vinyl-terminated 3- and 8-carbon compounds were generated on Si substrates and reacted at room temperature with approximately 1 ppm gaseous O(3). A combination of atomic force microscopy (AFM), scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used to study the surface composition and morphology after oxidation. A distribution of large ( approximately 0.1-10 microm) organic aggregates was formed, while the surrounding substrate became depleted of carbon compared to the unreacted SAM. This highly unusual result establishes that the mechanism of ozonolysis of alkene SAMs must have a channel that is unique compared to that in the gas phase or in solution, and may involve polymerization induced by the Criegee intermediate (CI). Oxidation at 60% RH led to the formation of a number of smaller aggregates, suggesting water intercepted the CI in competition with aggregate formation. The uptake of water, measured using transmission FTIR, was not increased upon oxidation of these films. In conjunction with literature reports of polymer formation from VOC-NO(x) photooxidations, these results suggest that formation of aggregates and polymers in the atmosphere is much more widespread than previously thought. The implications for the ozonolysis of alkenes on surfaces, for the transformation of organics in the atmosphere, and for the reactions and stability of unsaturated SAMs, are discussed.     

Evaluating UV-B effects and EDU protection in soybean leaves using fluorescence

A growth-chamber experiment was conducted to evaluate whether ethylenenediurea (EDU), a chemical shown to be protective against ozone pollution, could ameliorate foliar damage induced by ultraviolet-B (UV-B) radiation exposure in 'Roanoke' soybean (Glycine max L.), a UV-B-sensitive cultivar, and whether these effects could be discriminated using fluorescence (F) observations. The experiment had four treatment groups: control; biologically effective UV-B (18 kJ m(-2) day(-1)); EDU (500 micromol mol(-1)); and both UV-B and EDU (UV/EDU). Measurements included photosynthetic pigments, F image system (FIS) images of adaxial surfaces in four spectral regions (blue, green, red and far-red) and F emission spectra of the pigment extracts produced at two excitation wavelengths, 280 nm (280EX) and 380 nm (380EX). Several F ratios from 280EX, 380EX and the FIS images successfully separated the low UV vs high EDU group responses based on means alone, with intermediate values for controls and the combined UV/EDU groups. A UV-B/blue emission ratio, F315/F420 (280EX), was correlated with chlorophyll content (microg cm(-2))(R = 0.88, P < 0.001), as was a ratio of emissions at two UV-A wavelengths: F330/F385 (280EX) (R = 0.87). These two 280EX ratios were also linearly correlated with emission ratios produced by 380EX, such as the far-red/green ratio, F730/F525 (380EX) (R = 0.92, P < 0.001), and clearly distinguished the UV-B and EDU groups separately, and which bracketed the similar intermediate responses of the UV/EDU and control groups. The FIS images additionally captured the following anatomical spatial patterns across the leaf surfaces: (1) emissions of UV-B-irradiated leaves were more uniform but lower in intensity than those of other groups; and (2) emissions of EDU-treated leaves exhibited the greatest variation in spatial patterns because veins had elevated blue F and leaf edges had enhanced red and far-red F. This experiment supports the hypothesis that EDU substantially ameliorated UV-B damage to foliage, a result that relied on the combined use of FIS images and emission spectra.     

Facile C21 functionalization through a novel functional group transfer reaction in 16 alpha,17 alpha-epoxy-3 beta-hydroxypregn-5-en-20-one and its applications

A novel functional group transfer reaction in 16 alpha,17 alpha-epoxy-3 beta-hydroxypregn-5-en-20-one by treatment with dry HCl affords 21-chloro-3 beta-hydroxy-pregn-5,16-dien-20-one, which has been utilized to obtain a number of C21-substituted derivatives.     

Synergistic Role of Bacterial Urease and Carbonic Anhydrase in Carbonate Mineralization

The investigation on the synergistic role of urease (UA) and carbonic anhydrase (CA) in biomineralization of calcium carbonate in Bacillus megaterium suggested that the precipitation of CaCO₃ is significantly faster in bacterial culture than in crude enzyme solutions. Calcite precipitation is significantly reduced when both the enzymes are inhibited in comparison with those of the individual enzyme inhibitions indicating that both UA and CA are crucial for efficient mineralization. Carbonic anhydrase plays a role in hydrating carbon dioxide to bicarbonate, while UA aids in maintaining the alkaline pH that promotes calcification process.     

Developing imprinted polymer nanoparticles for the selective separation of antidiabetic drugs

In this study, new molecularly imprinted polymer (MIP) nanoparticles are designed for selective recognition of different drugs used for the treatment of type 2 diabetes mellitus, i.e. sitagliptin (SG) and metformin (MF). The SG‐ and MF‐imprinted polymer nanoparticles are synthesized by free‐radical initiated polymerization of the functional monomers: methacrylic acid and methyl methacrylate; and the crosslinker: ethylene glycol dimethacrylate. The surface morphology of resultant MIP nanoparticles is studied by atomic force microscopy. Fourier transform infrared spectra of MIP nanoparticles suggest the presence of reversible, non‐covalent interactions between the template and the polymer. The effect of pH on the rebinding of antidiabetic drugs with SG‐ and MF‐imprinted polymers is investigated to determine the optimal experimental conditions. The molecular recognition characteristics of SG‐ and MF‐imprinted polymers for the respective drug targets are determined at low concentrations of SG (50–150 ppm) and MF (5–100 ppm). In both cases, the MIP nanoparticles exhibit higher binding response compared to non‐imprinted polymers. Furthermore, the MIPs demonstrate high selectivity with four fold higher responses toward imprinted drugs targets, respectively. Recycled MIP nanoparticles retain 90% of their drug‐binding efficiency, which makes them suitable for successive analyses with significantly preserved recognition features.