Different polyphenolic components of soft fruits inhibit alpha-amylase and alpha-glucosidase

Polyphenol-rich extracts from soft fruits were tested for their ability to inhibit alpha-amylase and alpha-glucosidase. All extracts tested caused some inhibition of alpha-amylase, but there was a 10-fold difference between the least and most effective extracts. Strawberry and raspberry extracts were more effective alpha-amylase inhibitors than blueberry, blackcurrant, or red cabbage. Conversely, alpha-glucosidase was more readily inhibited by blueberry and blackcurrant extracts. The extent of inhibition of alpha-glucosidase was related to their anthocyanin content. For example, blueberry and blackcurrant extracts, which have the highest anthocyanin content, were the most effective inhibitors of alpha-glucosidase. The extracts most effective in inhibiting alpha-amylase (strawberry and raspberry) contain appreciable amounts of soluble tannins. Other tannin-rich extracts (red grape, red wine, and green tea) were also effective inhibitors of alpha-amylase. Indeed, removing tannins from strawberry extracts with gelatin also removed inhibition. Fractionation of raspberry extracts on Sephadex LH-20 produced an unbound fraction enriched in anthocyanins and a bound fraction enriched in tannin-like polyphenols. The unbound anthocyanin-enriched fraction was more effective against alpha-glucosidase than the original extract, whereas the alpha-amylase inhibitors were concentrated in the bound fraction. The LH-20 bound sample was separated by preparative HPLC, and fractions were assayed for inhibition of alpha-amylase. The inhibitory components were identified as ellagitannins using LC-MS-MS. This study suggests that different polyphenolic components of fruits may influence different steps in starch digestion in a synergistic manner.     

Anthocyanin-flavanol condensation products from black currant (Ribes nigrum L.)

Putative flavanol-anthocyanin condensation products were detected in a polyphenol-rich concentrate from black currant (Ribes nigrum L.). These compounds had UV-vis spectra similar to those of delphinidin-3-O-rutinoside and cyanidin-3-O-rutinoside, but eluted before all previously described anthocyanins on reversed phase HPLC. Mass spectrometric data indicated that they were rutinoside derivatives of novel aglycons 304 amu greater than delphinidin and cyanidin, respectively. The compounds were partly purified by semipreparative HPLC and gave MS and MS2 spectra consistent with anthocyanin rutinosides covalently linked to epigallocatechin or gallocatechin. These compounds are similar in structure to compounds thought to influence color and quality in red wines and strawberry juice products. There was also evidence for the presence of a range of other flavanol-anthocyanin condensation products. The compounds were present at differing levels in juices of 10 black currant varieties, which were roughly correlated to the content of the parent anthocyanins. The flavanol-anthocyanin products were present in polyphenol-enriched concentrates obtained by solid phase extraction, in commercially produced concentrates, and in fresh extracts of black currants. This suggests that the compounds were not artifacts formed during concentration or purification. However, differences in their comparative contents may be related to the lability of the parent anthocyanins during processing. Although present at low levels, the flavanol-anthocyanin products may influence color or quality parameters of black currant juices, and they may confer enhanced stability to the biological activities reported for their anthocyanin parents.     

Removal of Dyes from Water Using a TiO2 Photocatalyst Supported on Black Sand

A TiO₂ photocatalyst was prepared by depositing silica and titanium dioxide on the surface of black sand that made the photocatalyst recoverable using a magnetic field. The magnetic photocatalyst was used to remove six aqueous dyes from water and the removal was attributed to both adsorption and photocatalytic oxidation. Removal by adsorption was more noticeable with the cationic dyes than with the anionic dyes. The difference was related to the electrostatic interaction between the charged dye molecular and the silica-occupied surface of the photocatalyst. Removal by photocatalytic oxidation occurred with anionic dyes, while it was not appreciable with cationic dyes. It was postulated that photocatalytic oxidation might have happened with cationic dyes as well, but the strong adsorption made the photocatalytic oxidation undetectable.     

Effects of elevated atmospheric CO2, prolonged summer drought and temperature increase on N2O and CH4 fluxes in a temperate heathland

In temperate regions, climate change is predicted to increase annual mean temperature and intensify the duration and frequency of summer droughts, which together with elevated atmospheric carbon dioxide (CO₂) concentrations, may affect the exchange of nitrous oxide (N₂O) and methane (CH₄) between terrestrial ecosystems and the atmosphere. We report results from the CLIMAITE experiment, where the effects of these three climate change parameters were investigated solely and in all combinations in a temperate heathland. Field measurements of N₂O and CH₄ fluxes took place 1-2 years after the climate change manipulations were initiated. The soil was generally a net sink for atmospheric CH₄. Elevated temperature (T) increased the CH₄ uptake by on average 10 μg C m⁻² h⁻¹, corresponding to a rise in the uptake rate of about 20%. However, during winter elevated CO₂ (CO₂) reduced the CH₄ uptake, which outweighed the positive effect of warming when analyzed across the study period. Emissions of N₂O were generally low (<10 μg N m⁻² h⁻¹). As single experimental factors, elevated CO₂, temperature and summer drought (D) had no major effect on the N₂O fluxes, but the combination of CO₂ and warming (TCO₂) stimulated N₂O emission, whereas the N₂O emission ceased when CO₂ was combined with drought (DCO₂). We suggest that these N₂O responses are related to increased rhizodeposition under elevated CO₂ combined with increased and reduced nitrogen turnover rates caused by warming and drought, respectively. The N₂O flux in the multifactor treatment TDCO₂ was not different from the ambient control treatment. Overall, our study suggests that in the future, CH₄ uptake may increase slightly, while N₂O emission will remain unchanged in temperate ecosystems on well-aerated soils. However, we propose that continued exposure to altered climate could potentially change the greenhouse gas flux pattern in the investigated heathland.     

Characteristic Fly-ash Particles from Oil-shale Combustion Found in Lake Sediments

Fly-ash particles accumulate in sediments and can be used to assess spatial distribution and temporal trends of atmospheric deposition of pollutants derived from high temperature combustion of fossil fuels. Previous work has concerned fly-ash derived from oil and coal. Oil-shale is the main fossil fuel used in Estonia and a major source of atmospheric pollution in the Baltic states. To assess if oil-shale power plants produce specific fly-ash particles, we used scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) to compare fly-ash particles from oil-shale combustion with particles from oil and coal combustion. Two types were analysed, large black (10–30 μm) and small glassy (<5 μm) spheroidal particles. Although particle morphology to some extent is indicative of the fuel burnt, morphological characters are not sufficient to differentiate between particles of different origin. However, our results indicate that with EDX analysis the fly-ash from oil-shale can be distinguished from oil and coal derived particles in environmental samples. Concentrations of large black and small glassy spheroidal fly-ash particles in a sediment core from an Estonian lake showed similar trends to oil-shale combustion statistics from Estonian power plants.     

PCB in a River System During Sediment Remediation

Remediation of 150 000 m³ of sediment containing400 kg PCB was performed by suction dredging in asmall lake in Sweden in the summers of 1993 and 1994.Upon project completion calculations indicated that97% of the PCB was deposited in a landfill withsubsequent low transport to the surroundings, andthat 2.9 kg was left in the lake sediment.Concentrations of PCB that were measured weekly in thewater leaving the lake were 12 ng/L (geometric mean)during dredging, not exceeding 30 ng/L and notsignificantly higher than in investigations preceedingthe remedial action. The concentration of PCB wasnegatively correlated to water discharge andpositively correlated to water temperature. PCBtransport in the river was correlated to waterdischarge but not to the dredging activity. Duringdredging of the most contaminated part of the lake,the dredging area was screened off by a geotextilesilt curtain that reduced leakage of PCB to the riverdownstream.     

The use of insulated time-domain reflectometry sensors to measure water content in highly saline soils

In a conducting medium, the energy of a time-domain reflectometry (TDR) pulse is dissipated and the signal is attenuated. Above a certain high conductivity, however, the signal is completely attenuated and the soil short-circuits the sensor. This behaviour of the signal with conductivity severely limits the TDR technique in measuring water content in highly saline soils. By reducing the direct contact between the conductive soil and the metallic sensor the energy of the pulse is better maintained. Different combinations were tried: we insulated the central wire, outer two wires, and all wires of a three-wire sensor with two different insulators. The first insulator was an adhesive polyethylene sheet usually used as a transparent cover and the second insulator was an adhesive tape. The insulated sensors were used to measure dielectric constants in non-saline soils and water and in saline soils. The sensors with the insulated centre wire preserve maximum energy and maintain a clear signal in saline soils. The insulating materials have very small dielectric constants. The TDR exerts a larger influence in the vicinity of the wires of the sensor during measurements. Therefore, the insulated sensor measures a dielectric constant which is smaller than the apparent dielectric constant of the surrounding medium. The type of insulating material also has an effect on the dielectric constant. Therefore, it is necessary to calibrate the sensors for the specific insulator. Received: 30 December 1996     

Reaction-driven restructuring of Rh-Pd and Pt-Pd core-shell nanoparticles

Heterogeneous catalysts that contain bimetallic nanoparticles may undergo segregation of the metals, driven by oxidizing and reducing environments. The structure and composition of core-shell Rh(0.5)Pd(0.5) and Pt(0.5)Pd(0.5) nanoparticle catalysts were studied in situ, during oxidizing, reducing, and catalytic reactions involving NO, O2, CO, and H2 by x-ray photoelectron spectroscopy at near-ambient pressure. The Rh(0.5)Pd(0.5) nanoparticles underwent dramatic and reversible changes in composition and chemical state in response to oxidizing or reducing conditions. In contrast, no substantial segregation of Pd or Pt atoms was found in Pt(0.5)Pd(0.5) nanoparticles. The different behaviors in restructuring and chemical response of Rh(0.5)Pd(0.5) and Pt(0.5)Pd(0.5) nanoparticle catalysts under the same reaction conditions illustrates the flexibility and tunability of the structure of bimetallic nanoparticle catalysts during catalytic reactions.