Comparison of pressurised fluid and ultrasonic extraction methods for analysis of plant antioxidants and their antioxidant capacity

The analytical method based on the high-performance liquid chromatography coupled with UV detection (HPLC/UV) for determination of selected antioxidants (i.e., esculetin, scopoletin, 7-hydroxycoumarine, rutin, xanthotoxin, 5-methoxypsoralen and quercetin) in plant material was developed. Pressurised fluid extraction (PFE) and ultrasonic extraction (USE) methods for the isolation of these compounds from ten real plant samples were used. Both extraction methods were optimised and compared to each other. For the proposed HPLC/UV method the LOQ values (limit of quantification) in the range from 22.7 (xanthotoxin) to 97.2 ng mL⁻¹ (rutin) were obtained. For all extracts the antioxidant capacity based on the reduction of free 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) was also determined. Results ranged from 82.04 to 94.43% of DPPH radical inhibition for PFE method and from 76.01 to 89.94% in the case of USE method.     

Selective Formation of Methyl α-Methylsulfanyl Dimethylphosphonothioacetate and Thiopropanoate by Phase Transfer Catalysis

The sulfanylation of methyl dimethylphosphonothioacetate was investigated by a phase transfer catalysis procedure which was shown to be superior to the noncatalytic method. The possibility of electrophilic substitution of the α-sulfanylated phosphonothioacetate to give a quaternary α-carbon atom is shown by the reaction with methyl iodide.

     

On the asymptotic behavior of a class of third order nonlinear neutral differential equations

The objective of this paper is to study asymptotic properties of the third-order neutral differential equation

Metadynamics in the conformational space nonlinearly dimensionally reduced by Isomap

Atomic motions in molecules are not linear. This infers that nonlinear dimensionality reduction methods can outperform linear ones in analysis of collective atomic motions. In addition, nonlinear collective motions can be used as potentially efficient guides for biased simulation techniques. Here we present a simulation with a bias potential acting in the directions of collective motions determined by a nonlinear dimensionality reduction method. Ad hoc generated conformations of trans,trans-1,2,4-trifluorocyclooctane were analyzed by Isomap method to map these 72-dimensional coordinates to three dimensions, as described by Brown and co-workers [J. Chem. Phys. 129, 064118 (2008)]. Metadynamics employing the three-dimensional embeddings as collective variables was applied to explore all relevant conformations of the studied system and to calculate its conformational free energy surface. The method sampled all relevant conformations (boat, boat-chair, and crown) and corresponding transition structures inaccessible by an unbiased simulation. This scheme allows to use essentially any parameter of the system as a collective variable in biased simulations. Moreover, the scheme we used for mapping out-of-sample conformations from the 72D to 3D space can be used as a general purpose mapping for dimensionality reduction, beyond the context of molecular modeling.     

Determination of 5-fluorouracil in hospital effluents

Cytostatic anticancer drugs are an increasingly important issue in the environmental debate, mainly due to the lack of knowledge about the fate of these toxic substances. Over the last decades, 5-fluorouracil (5-FU) has been one of the most frequently used antineoplastic agents and may, therefore, be regarded as one of the pilot substances for environmental contamination. As a prerequisite for these investigations, a method for the determination of 5-FU in hospital effluents has been developed. Waste water samples were enriched by solid-phase extraction on ENV⁺ columns (concentration factor 500) and analysed by capillary electrophoresis using a buffer containing 80% 160 mM sodium borate buffer (pH 9.5) and 20% acetonitrile (v/v). This method is applicable within the range 5–500 g 5-FU L^–1. The standard curve (correlation coefficient >0.99) was linear with recovery rates from 80 to 96% and an accuracy from 9.0 to 20% (intra-assay standard deviation 0.7–8.9%; inter-assay standard deviation 2.2–9.5%). Based on the consumption of 5-FU in oncologic departments and the detection limit of 1.7 g L^–1, this method covers the range necessary to evaluate 5-FU in hospital effluents. The applicability of the method was proven by chemical analysis of real hospital waste water samples. Obtained over a time period of 1 month (range 20–122 g 5-FU L^–1), the results were similar to those calculated by an input–output model. The presented method provides an analytical tool necessary to face the monitoring of environmental contamination problems.Abbreviations 5-FU 5-Fluorouracil - OECD Organization for economic cooperation and development     

Molecular Shield for Protection of Buckwheat Plants from UV-B Radiation

Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) and common buckwheat (Fagopyrum esculentum Moench) are adapted to growing in harsh conditions of high altitudes. Ultraviolet radiation at high altitudes strongly impacts plant growth and development. Under the influence of ultraviolet radiation, protecting substances are synthesized in plants. The synthesis of UV-B defense metabolites is genetically conditioned, and their quantity depends on the intensity of the ultraviolet radiation to which the plants and plant parts are exposed. These substances include flavonoids, and especially rutin. Other substances with aromatic rings of six carbon atoms have a similar function, including fagopyrin, the metabolite specific for buckwheat. Defensive substances are formed in the leaves and flowers of common and Tartary buckwheat, up to about the same concentration in both species. In comparison, the concentration of rutin in the grain of Tartary buckwheat is much higher than in common buckwheat. Flavonoids also have other functions in plants so that they can protect them from pests and diseases. After crushing the grains, rutin is exposed to contact with the molecules of rutin-degrading enzymes. In an environment with the necessary humidity, rutin is turned into bitter quercetin under the action of rutin-degrading enzymes. This bitterness has a deterrent effect against pests. Moreover, flavonoids have important functions in human nutrition to prevent several chronic diseases, including obesity, cardiovascular diseases, gallstone formation, and hypertension.     

An efficient microwave-assisted synthesis and biological properties of polysubstituted pyrimidinyl- and 1,3,5-triazinylphosphonic acids

Polysubstituted pyrimidinylphosphonic and 1,3,5-triazinylphosphonic acids with potential biological properties were prepared in high yields by the microwave-assisted Michaelis–Arbuzov reaction of trialkyl phosphite with the corresponding halopyrimidines and halo-1,3,5-triazines, respectively, followed by the standard deprotection of the phosphonate group using TMSBr in acetonitrile. 4,6-Diamino-5-chloropyrimidin-2-ylphosphonic acid (7a) was found to exhibit a weak to moderate anti-influenza activity (28–50 μM) and may represent a novel hit for further SAR studies and antiviral improvement.     

Polymer Carriers for Anticancer Drugs Targeted to EGF Receptor

A novel actively targeted polymer carrier for anticancer drugs based on an N‐(2‐hydroxypropyl)methacrylamide copolymer (PHPMA) is proposed. An oligopeptide sequence GE7, attached to the polymer, is a specific ligand for the EGF receptor overexpressed on most tumor cells. Co‐attachment of selected chemotherapeutics will therefore lead to formation of tumor‐specific polymer therapeutics, further enhanced by the EPR effect. FACS measurements prove elevated binding activity of the fluorescently labeled PHPMA/GE7 conjugate in EGFR‐rich cells (FaDu, MCF‐7), compared to conjugates of scrambled peptides. Cell lines with low EGFR level (SW620, B16F10) bind the GE7 conjugate significantly less.