Current trends in isolation, separation, determination and identification of isoflavones: a review

Isoflavones are natural substances which elicit a number of physiological effects in living organisms. The substances are synthesized in plant tissues as protective agents against biotic stress (i. e. bacterial infection). Isoflavones are also an important dietary constituent in human nutrition. Modern trends in studies of isoflavones in plant materials and foodstuffs and procedures for chemical analyses of isoflavones in human body fluids and plant tissues are discussed in this review. Highly effective extraction and purification techniques, i. e. solid-phase extraction, accelerated-solvent extraction, and Soxhlet extraction, are presented. Latest procedures in chromatographic separation of isoflavones that apply different types of sorbents are described. Immunochemical analysis, electrochemical sensing of isoflavones, and spectrometric and other analytical techniques and their applications are also mentioned. Special attention is paid to the highly selective and sensitive technique of mass spectrometry and its application for identification of isoflavones and their glucosides in plants. Studies of interactions of isoflavones with cell receptors and a number of biologically active substances such as DNA and proteins are described. The review does not intend to give a complete overview of the topics considered but rather to present modern and most recent methods used in studies of isoflavones.     

A combination of statistical and analytical evaluation methods as a new optimization strategy for the quantification of pharmaceutical residues in sewage effluent

In this study, a new solid-phase microextraction (SPME) method for simultaneous extraction of pharmaceutical compounds with acidic and basic characteristics (ibuprofen, fenoprofen, diclofenac, diazepam and loratadine) from residual water samples is proposed. In this procedure, the extraction is processed using two distinct sample pH values. The extraction is begun at pH 2.5 to promote the sorption of acidic pharmaceuticals and after 35 min the sample pH is changed to 7.0 by adding 0.4 mol L⁻¹ disodium hydrogenphosphate, so that the basic compounds can be sorbed by the fiber (20 min). The pH change is performed without interruption of the extraction process. A comparison between the proposed method and the SPME method applied to each group of the target compounds was performed. Gas chromatography coupled to mass spectrometry was used for separation and detection of analytes. The extraction conditions for the three methods were optimized using full factorial experimental design, response surface through a Doehlert matrix and central composite design. Limits of detection (0.02-0.43 μg L⁻¹) and correlation coefficients (0.9970-0.9998) were determined for the three methods. The proposed extraction procedure was applied to samples of sewage treatment plant effluent and untreated wastewater. Recovery and relative standard deviation values ranged from 67 to 116% and 4.6 to 14.5%, respectively, for all compounds studied. Modification of sample pH during the extraction procedure was shown to be an excellent option for all of the compounds and may be extended to the simultaneous extraction of other compounds with different acid-base characteristics.     

Decomposition of dinuclear manganese complexes for the preparation of nanostructured oxide materials

The crystal structures of several dinuclear complexes of manganese are reported, and the decomposition and analysis of the nanostructured products derived from them are presented. 1,4,7,10-Tetraazacyclododecane (cyclen) forms dinuclear complexes 1-4 containing doubly oxo-bridged or oxo-acetato bridging ligands depending on the manganese salt used for the reaction. Doubly oxo-bridged 1 crystallizes in the orthorhombic space group Pnma, a = 22.3850(14) A, b = 9.1934(5) A, c = 13.2424(10) A, V = 2725.2(3) A(3). 2, containing [Mn(SCN)5](3-) conteranions, crystallizes in monoclinic space group I2/a with a = 18.2699(10) A, b = 11.2384(6) A, c = 18.6432(9) A, alpha = 90.00 degrees, beta = 114.510(6) degrees, gamma = 90.00 degrees, V = 3483.0(3) A(3). Oxo-acetato-bridged 3 crystallizes in orthorhombic space group Pca21, a = 13.9322(11) A, b = 16.2332(13) A, c = 14.6794(8) A, V = 3320.0(4) A(3). Compound 4 consists of a templated quasi-one-dimensional manganese oxalate crystallized in the triclinic space group P1, a = 9.5442(11) A, b = 10.3758(10) A, c = 21.851(2) A, alpha = 83.720(12) degrees, beta = 80.106(13) degrees, gamma = 85.457(13) degrees, V = 2114.9(4) A(3). Compounds 1, 3, and 4 decompose to nanostructured oxide materials, which may be isolated in bulk as lamellar-structured particles or microspheres or deposited on substrates.     

Modifying the 5′‐Cap for Click Reactions of Eukaryotic mRNA and To Tune Translation Efficiency in Living Cells

The 5′‐cap is a hallmark of eukaryotic mRNAs and plays fundamental roles in RNA metabolism, ranging from quality control to export and translation. Modifying the 5′‐cap may thus enable modulation of the underlying processes and investigation or tuning of several biological functions. A straightforward approach is presented for the efficient production of a range of N7‐modified caps based on the highly promiscuous methyltransferase Ecm1. We show that these, as well as N²‐modified 5′‐caps, can be used to tune translation of the respective mRNAs both in vitro and in cells. Appropriate modifications allow subsequent bioorthogonal chemistry, as demonstrated by intracellular live‐cell labeling of a target mRNA. The efficient and versatile N7 manipulation of the mRNA cap makes mRNAs amenable to both modulation of their biological function and intracellular labeling, and represents a valuable addition to the chemical biology toolbox.     

Supramolecular triad and pentad composed of zinc-porphyrin(s), oxoporphyrinogen, and fullerene(s): design and electron-transfer studies

By adopting a "covalent-coordinate" bonding approach, novel supramolecular pentad and triad molecules composed of zinc-porphyrin(s), fullerene(s), and oxoporphyrinogen redox-/photoactive entities have been constructed, and also characterized by means of spectral and electrochemical techniques. The geometry and electronic structures of the pentad and the triad were deduced by means of DFT calculations. Free-energy calculations suggested that the photoinduced electron/energy transfer from the zinc-porphyrin (ZnP) singlet-excited state to the imidazole modified fullerene (ImC(60)) acceptor and oxoporphyrinogen (OxP) entities is feasible for both the triad and the pentad. The charge-separation rates (k(CS)) determined from picosecond time-resolved emission studies were higher for pentad (C(60)Im:ZnP)(2)-OxP than for the corresponding triad, C(60)Im:ZnP-OxP. A comparison of the k(CS) values previously reported for the covalently linked bis(zinc-porphyrin)-oxoporphyrinogen triad suggests that employing a fullerene acceptor improves the electron-transfer rates. Nanosecond transient absorption studies provide evidence for the occurrence of electron-transfer processes. Lifetimes of the radical ion pairs (tau(RIP)) are in the range of hundreds of nanoseconds, which indicates that there is charge stabilization in the supramolecular systems.     

Tautomerism in novel oxocorrologens

A novel corrole-type macrocycle, oxocorrologen (2), substituted with hemiquinone groups, has been synthesized. It was found to undergo multiple tautomerism of its exchangeable protons between electronegative atom sites at the macrocyclic core (nitrogen atoms) and periphery (phenol oxygen atoms). Alkylation at one macrocyclic nitrogen atom with a 4-nitrobenzyl group gave 3, which can exist in only two tautomeric forms depending on the solvent. Tautomerism has been studied by means of (1)H NMR spectroscopy in a variety of solvents and solvent mixtures. Tautomer structure assignments have been supported by DFT calculations of the relative energies of the tautomers. X-ray crystallography of the N-nitrobenzyl derivative has revealed that intramolecular hydrogen bonding may be responsible for stabilizing the observed tautomers. The solvent dependence of the tautomerism of 2 and 3 confers solvatochromism. Electrochemical measurements on 2 and 3 in their respective quinone forms have revealed irreversible processes, but indicate that they are both electron-deficient with a small HOMO-LUMO gap and first reduction potentials close to those of fullerene electron acceptors.     

Dolphin (Tursiops truncatus) echoic angular discrimination: effects of object separation and complexity

A bottlenose dolphin was tested on its ability to echoically discriminate horizontal angular differences between arrays of vertically oriented air-filled PVC rods. The blindfolded dolphin was required to station in a submerged hoop 2 radial m from the stimuli and indicate if an array with two rods (S+) was to the right or the left of a single rod (S-). The angular separation between the two rods (thetaw) was held constant within each experiment while the angle between the S+ and the S-stimuli (thetab) varied to produce angular differences (deltatheta= thetab-thetaw) ranging from 0.25 to 4 degrees. In experiment I, thetaw was maintained at 2 degrees and in experiment II, thetaw was maintained at 4 degrees. Resulting 75% correct thresholds (method of constant stimuli) were 1.5 and 0.7 degrees, respectively. The two main findings of this study are: (1) decreasing the number of targets does not aid in localization, and (2) increasing the space between the rods enhances localization. Taken as a whole, the experiments suggest dolphins have a well-developed ability to resolve spatial information through sonar.