Microwave‐assisted water extraction of green tea polyphenols

Introduction – Green tea, a popular drink with beneficial health properties, is a rich source of specific flavanols (polyphenols). There is a special interest in the water extraction of green tea polyphenols since the composition of the corresponding extracts is expected to reflect the one of green tea infusions consumed worldwide. Objective – To develop a microwave‐assisted water extraction (MWE) of green tea polyphenols. Methodology – MWE of green tea polyphenols has been investigated as an alternative to water extraction under conventional heating (CWE). The experimental conditions were selected after consideration of both temperature and extraction time. The efficiency and selectivity of the process were determined in terms of extraction time, total phenolic content, chemical composition (HPLC‐MS analysis) and antioxidant activity of the extracts. Results – By MWE (80°C, 30 min), the flavanol content of the extract reached 97.46 (± 0.08) mg of catechin equivalent/g of green tea extract, vs. only 83.06 (± 0.08) by CWE (80°C, 45 min). In particular, the concentration of the most bioactive flavanol EGCG was 77.14 (± 0.26) mg of catechin equivalent/g of green tea extract obtained by MWE, vs 64.18 (± 0.26) mg/g by CWE. Conclusion – MWE appears more efficient than CWE at both 80 and 100°C, particularly for the extraction of flavanols and hydroxycinnamic acids. Although MWE at 100°C typically affords higher yields in total phenols, MWE at 80°C appears more convenient for the extraction of the green tea‐specific and chemically sensitive flavanols. Copyright © 2009 John Wiley & Sons, Ltd.     

The so‐called primitive genera of Genisteae (Fabaceae): systematic and phyletic considerations based on karyological data

A karyological analysis of the so‐called primitive genera of Genisteae has shown that they have a relatively homogeneous chromosome complement: all species tend to have a somatic chromosome number 2n = 48, which can increase to 2n = 52, presumably as a result of hyperaneuploidy. Karyological data suggest that Argyrocytisus, Cytisophyllum and Petteria may be considered as distinct genera rather than being assigned to Cytisus, with 2n = 52 for the first of these and 2n = 50 for the other two genera. They may be interpreted as relict monotypic genera as a result of the presence of a stabilized aneuploidy. Karyological characters exclude a recent origin of Genisteae from Thermopsideae. On the contrary, they are consistent with the hypothesis that Genisteae and Thermopsideae are independently derived from a basic papilionoid stock, of which present day Sophoreae are the remainder. At least two lines would lead from Sophoreae to the taxa of the ‘genistoid alliance’, one to Thermopsideae and the other ‘podalyrioid alliances’ (Podalyrieae and Mirbelieae), with the prevailing basic number of x = 9, and the other to Genisteae, with a basic number of x = 12 persisting in some present day genera, including Cytisus s.l. From this lineage, a wide range of secondary basic numbers has been formed, mostly by descending aneuploidy. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 160 , 232–248.     

Effects of depth and bottom communities on the distribution of highly territorial reef fish in the northwestern region of Cuba

The main goal of the study was to investigate changes in reef fish species abundance and its correlation with selected environmental variables. Three main questions guided the analyses: (i) Do the analytical methods have a significant influence on the results; (ii) What are the main assemblage variation axes; and (iii) What are the factors correlating best with assemblage composition. Highly territorial fish assemblages of several coral reefs along the northwestern region of Cuba were assessed using a stationary point visual census technique. A total of 39 701 individuals of 26 species from the families Chaetodontidae, Labridae and Pomacentridae were counted in 841 censuses; almost 80% of the fish belonged to just four species: bluehead (Thalassoma bifasciatum), bicolor damselfish (Stegastes partitus), slippery dick (Halichoeres bivittatus) and blue chromis (Chromis cyanea). Several multivariate techniques (cluster analysis, non‐metric multidimensional scaling and canonical correspondence analysis) were used to explore main patterns in assemblage composition variation. It was found that the results did not differ significantly when analyzing the same data set. Furthermore, it was shown that the combined use of different multivariate techniques enhanced the interpretation of fish assemblage composition changes. Depth was the main variable explaining variation in the composition of fish assemblages in the studied reefs. The densities of corals and gorgonians were also strongly associated with depth. Sponge density made an additional significant contribution to the explanatory model. Results of this research could be used as a baseline reference for future analyses of the impact of human actions in the study area. (e.g. oil spills, change in fishing intensity, other pollution events, tourism development).     

MICROMORPHOGENESIS DURING DIATOM WALL FORMATION PRODUCES SILICEOUS NANOSTRUCTURES WITH DIFFERENT PROPERTIES1

Micromorphogenesis within the silica deposition vesicle (SDV) of the diatom Pinnularia viridis (Nitzsh) Ehrenb. resulted in distinct silica nanostructures and layers within forming valves and girdle bands. These siliceous components were similarly disclosed following alkaline etching of mature valves/girdle bands, where their different susceptibilities to dissolution over time resulted from apparent differences in silica density and/or chemistry. The bulk of silica appeared to be deposited at the interface of the forming valve or girdle band with the silicalemma and occurred by the outward expansion of microfibrils of silica that aligned perpendicularly to the silicalemma. Microfibrils originated from both sides of the “silica lamella,” the first nanostructure formed within the SDV, and several silica species of distinct nanostructure and density resulted, including distinctive inner and outermost silica “coverings” of mature valves/girdle bands and the central and terminal nodules. Not all silica deposition and micromorphogenesis occurred in contact with the expanding silicalemma, but was somehow directed within the SDV cavity, and resulted in the distinct silica layers that lined the raphe fissures and poroids. Following alkaline etching, the inner surfaces of valves/girdle bands, as well as the silica layers lining the raphes, poroids, and slits, were determined to be significantly more resistant to alkaline etching than the exterior surfaces, while the outer silica coating and the nodules were quickly dissolved. The processes of micromorphogenesis must have exerted precise control over the chemical nature of the silica formed at different positions within the SDV and affected the overall structure and function of the diatom wall.     

The Role of Electron Affinity in Determining Whether Fullerenes Catalyze or Inhibit Photooxidation of Polymers for Solar Cells

Understanding the stability and degradation mechanisms of organic solar materials is critically important to achieving long device lifetimes. Here, an investigation of the photodegradation of polymer:fullerene blend films exposed to ambient conditions for a variety of polymer and fullerene derivative combinations is presented. Despite the wide range in polymer stabilities to photodegradation, the rate of irreversible polymer photobleaching in blend films is found to consistently and dramatically increase with decreasing electron affinity of the fullerene derivative. Furthermore, blends containing fullerenes with the smallest electron affinities photobleached at a faster rate than films of the pure polymer. These observations can be explained by a mechanism where both the polymer and fullerene donate photogenerated electrons to diatomic oxygen to form the superoxide radical anion which degrades the polymer.     

Insecticidal activities of Ginkgo biloba seed coat extracts against Spodoptera exigua (Lepidoptera: Noctuidae)

The present study relates to a methanol extract of the seed coat of Ginkgo biloba, and tested particularly on the third instar larvae of Spodoptera exigua. The extract was found to have an inhibitory effect on the growth of the larvae besides bringing a change in the nutrient reserves in the body of the insect. Topical application of five different doses of the methanol extract resulted in a mortal effect to third instar larvae of S. exigua that is very much dependent on the dose as well as duration of exposure. Lower doses revealed lower mortality after 24 h of application. At doses of 1.00, 2.00, 4.00, 8.00 and 16.00 ng/larva, mortalities were 9.25, 26.07, 50.32, 56.28 and 92.44%, respectively. The dose for 50% mortality (LD₅₀) of methanol extracts by applied by a topical method with 1 µL of acetone solution was 1.92 ng/larva. Nutrient reserves like protein, glycogen and lipid are known to regulate pupation and adult emergence. These reserves have been found to be lower in treated larvae, indicating the insecticidal role of methanol extracts from G. biloba against third instar larvae of S. exigua.     

Choice of hydrogen uptake (Hup) status in legume‐rhizobia symbioses

The H₂ is an obligate by-product of N-fixation. Recycling of H₂ through uptake hydrogenase (Hup) inside the root nodules of leguminous plants is often considered an advantage for plants. However, many of the rhizobium-legume symbioses found in nature, especially those used in agriculture are shown to be Hup⁻, with the plants releasing H₂ produced by nitrogenase activity from root nodules into the surrounding rhizosphere. Recent studies have suggested that, H₂ induces plant-growth-promoting rhizobacteria, which may explain the widespread of Hup⁻ symbioses in spite of the low energy efficiency of such associations. Wild legumes grown in Nova Scotia, Canada, were surveyed to determine if any plant-growth characteristics could give an indication of Hup choice in leguminous plants. Out of the plants sampled, two legumes, Securigera varia and Vicia cracca, showed Hup⁺ associations. Securigera varia exhibited robust root structure as compared with the other plants surveyed. Data from the literature and the results from this study suggested that plants with established root systems are more likely to form the energy-efficient Hup⁺ symbiotic relationships with rhizobia. Conversely, Hup⁻ associations could be beneficial to leguminous plants due to H₂-oxidizing plant-growth-promoting rhizobacteria that allow plants to compete successfully, early in the growing season. However, some nodules from V. cracca tested Hup⁺, while others were Hup⁻. This was similar to that observed in Glycine max and Pisum sativum, giving reason to believe that Hup choice might be affected by various internal and environmental factors.     

Raman spectroscopy for the non‐contact and non‐destructive monitoring of collagen damage within tissues

The non‐destructive and label‐free monitoring of extracellular matrix (ECM) remodeling and degradation processes is a great challenge. Raman spectroscopy is a non‐contact method that offers the possibility to analyze ECM in situ without the need for tissue processing. Here, we employed Raman spectroscopy for the detection of heart valve ECM, focusing on collagen fibers. We screened the leaflets of porcine aortic valves either directly after dissection or after treatment with collagenase. By comparing the fingerprint region of the Raman spectra of control and treated tissues (400–1800 cm^–1), we detected no significant differences based on Raman shifts; however, we found that increasing collagen degradation translated into decreasing Raman signal intensities. After these proof‐of‐principal experiments, we compared Raman spectra of native and cryopreserved valve tissues and revealed that the signal intensities of the frozen samples were significantly lower compared to those of native tissues, similar to the data seen in the enzymatically‐degraded tissues. In conclusion, our data demonstrate that Raman microscopy is a promising, non‐destructive and non‐contact tool to probe ECM state in situ. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Existence of memory in membrane channels: analysis of ion current through a voltage‐dependent potassium single channel

Ion current fluctuation of voltage‐dependent potassium channel in LβT2 cells has been investigated by autocorrelation function and DFA (detrended fluctuation analysis) methods. The calculation of the autocorrelation function exponent and DFA exponent of the sample was based on the digital signals or the 0–1 series corresponding to closing and opening of channels after routine evolution, rather than the sequence of sojourn times. The persistent character of the correlation of the time series was evident from the slow decay of the autocorrelation function. DFA exponent α was significantly greater than 0.5. The main outcome has been the demonstration of the existence of memory in this ion channel. Thus, the ion channel current fluctuation provided information about the kinetics of the channel protein. The result suggests the correlation character of the ion channel protein non‐linear kinetics indicates whether the channel is open or not.