Identification of acylated xanthone glycosides by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry in positive and negative modes from the lichen Umbilicaria proboscidea

The xanthoside composition of the crude extract of Umbilicaria proboscidea (L.) Schrader was characterized using LC-UV diode array detection and LC-atmospheric pressure chemical ionization (APCI) MS methods. The presence of acylated xanthone-O-glucosides was determined by both positive and negative ion LC-APCI-MS methods. Based on UV and MS spectral data and NMR spectroscopy, a total of 14 compounds (6-O-acylated umbilicaxanthosides A and B) were identified in U. proboscidea for the first time. In order to further develop the applicability of LC-MS techniques in phytochemical characterization, the effect of different ionization energy on fragmentation was studied using APCI. The optimal ionization conditions were achieved in positive ion APCI by using ammonium acetate buffer and in negative ion APCI by using formic acid (pH 4).     

Random replicators with high-order interactions

We use tools of the equilibrium statistical mechanics of disordered systems to study analytically the statistical properties of an ecosystem composed of N species interacting via random mutual interactions, as well as via deterministic self-interactions of order p>/=2. We show that the main effect of increasing the order of the interactions among the species is to make the system less competitive, in the sense that the fraction of extinct species is greatly reduced. In addition, we find that for p>2 there is a threshold value which gives a lower bound to the concentration of the surviving species, preventing then the existence of rare species and, consequently, increasing the robustness of the ecosystem to external perturbations.     

Nitrogen heterocycles from trimethylbenzenes

The reaction between 1,2,4‐trimethylbenzene 1 , isobutyric aldehyde, and cyanoacetic ester afforded a mixture of three products: 3,3,5,6,8‐ pentamethyl‐1,2,3,4‐tetraisoquinolylidene‐1‐acetic acid ether ( 2 ) and its 3,3,5,6,7‐pentamethyl‐( 3 )‐ and 3,3,6,7,8‐pentamethyl‐1,2,3,4‐tetraisoquinolyli‐ dene‐1‐acetic acid ether isomers ( 3 ) in ratio 1:5:1. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:471–476, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20045     

Direct heterocyclization of benzocrown ethers

The synthesis of novel 3,3‐dialkyl‐3,4‐dihydroisoquinoline derivatives via direct heterocyclization of benzocrown ethers is described. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:192–195, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20092     

Quantification of plasmalogen, alkylacyl and diacyl glycerophospholipids by micro-thin-layer chromatography

A method for the determination of plasmalogen, alkylacyl and diacyl glycerophospholipids based on mild alkaline deacylation and acid hydrolysis of plasmalogens on plates with subsequent micro-thin-layer chromatography on silica gel is presented. It is effective in quantifying alkyl and alkenyl analogues of phosphatidylethanolamine and phosphatidylcholine at concentrations up to 0.1% (of the total of the forms in individual classes of phospholipids.     

The colleflaccinosides, two chiral bianthraquinone glycosides with antitumor activity from the lichen Collema flaccidum collected in Israel and Russia

Colleflaccinosides A and B, two chiral bianthraquinone glycosides from the two geographical varieties of lichen Collema flaccidum collected in Russia and Israel have been isolated as new natural products. Their structures were elucidated using UV, CD, IR, MS, 1D and 2D NMR spectral data, and chemical degradation. The colleflaccinosides B had significant antitumor activity in the crown gall tumor inhibition test.     

Synthesis of substituted pyrroles in the glaser reaction

The substituted pyrroles and dipyrroles along with diacetylenes and cumulenes have been synthesized in high yields using a new synthetic method under mild reaction conditions using the Glaser coupling reaction. Although diacetylenes are formed from 2‐propargyl‐1,3‐dicarbonyl compounds having electron‐donors substituents such as Ph or OEt, only polyfunctional substituted cumulenes are formed from those compounds under the modified conditions. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:66–73, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20184     

Maturation of auditory temporal integration and inhibition assessed with event-related potentials (ERPs)

Background

We examined development of auditory temporal integration and inhibition by assessing electrophysiological responses to tone pairs separated by interstimulus intervals (ISIs) of 25, 50, 100, 200, 400, and 800 ms in 28 children aged 7 to 9 years, and 15 adults.

Results

In adults a distinct neural response was elicited to tones presented at ISIs of 25 ms or longer, whereas in children this was only seen in response to tones presented at ISIs above 100 ms. In adults, late N1 amplitude was larger for the second tone of the tone pair when separated by ISIs as short as 100 ms, consistent with the perceptual integration of successive stimuli within the temporal window of integration. In contrast, children showed enhanced negativity only when tone pairs were separated by ISIs of 200 ms. In children, the amplitude of the P1 component was attenuated at ISIs below 200 ms, consistent with a refractory process.

Conclusions

These results indicate that adults integrate sequential auditory information into smaller temporal segments than children. These results suggest that there are marked maturational changes from childhood to adulthood in the perceptual processes underpinning the grouping of incoming auditory sensory information, and that electrophysiological measures provide a sensitive, non-invasive method allowing further examination of these changes.     

A new approach to synthesis of 3,3‐dialkyl‐3,4‐dihydroisoquinoline derivatives

The synthesis of 3,3‐dialkyl‐3,4‐dihydroisoquinolines via heterocyclization in three‐component reaction of an activated arene with isobutyraldehyde and nitriles is described. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:486–493, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20049     

Tetratriacontanonaenoic acid, first natural acid with nine double bonds isolated from a crustacean Bathynella natans

The very-long-chain polyunsaturated fatty acid—allZ-4,7,10,13,16,19,22,25,28-tetratriacontanonaenoic acid was determined and identified in the freshwater crustacean species Bathynella natans living in caves of central Europe by means of liquid chromatography—mass spectrometry with atmospheric pressure chemical ionization. The full structure was elucidated by using extensive spectroscopic analysis (¹H and ¹³C NMR, MS, IR and UV) including a chemical method. This acid was described in nature for the first time. A hypothesis is suggested for its origin and biosynthesis.