bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bidesmosidic Oleanane Saponins from Xerospermum noronhianum
Authors: Jean Tan Pei , Shaari Khozirah , Paetz Christian , Ismail Intan Safinar , Abas Faridah , Lajis Nordin H. , Ahmad Viqar Uddin 
Published: October 2009

AbstractThree new oleanane‐type triterpenoid saponins, 3‐O‐(α‐L‐rhamnopyranosyl(1→2)‐β‐D‐fucopyranosyl)‐28‐O‐{[α‐L‐rhamnopyranosyl(1→2)] [β‐D‐fucopyranosyl(1→6)]‐β‐D‐glucopyranosyl} oleanolic acid (1), 3‐O‐[α‐L‐rhamnopyranosyl(1→3)‐β‐D‐fucopyranosyl]‐28‐O‐[α‐L‐rhamnopyranosyl(1→4)‐β‐D‐glucopyranosyl] oleanolic acid (2), and 3‐O‐{α‐L‐rhamnopyranosyl(1→2)‐[3′,4′‐diacetoxy‐β‐D‐fucopyranosyl]}‐28‐O‐[α‐L‐rhamnopyranosyl(1→2)‐β‐D‐glucopyranosyl] oleanolic acid (3) have been isolated from the stems of Xerospermum noronhianum. The structures of the saponins were determined as a series of bidesmosidic oleanane saponins based on spectral evidence. The anticholinesterase activity of the saponins 1–3 was also evaluated.
Photochemical Reactions of Regioisomeric 2,2‐Dimethyl‐5,5‐diphenyl‐ and 5,5‐Dimethyl‐2,2‐diphenyl‐Substituted Diazo Ketones of a Tetrahydrofuran Series
Authors: Rodina Ludmila L. , Malashikhin Sergey A. , Galkina Olesya S. , Nikolaev Valerij A. 
Published: October 2009

AbstractThe principal direction of conventional photolysis of the regioisomeric 2,2‐dimethyl‐5,5‐diphenyl‐ and 5,5‐dimethyl‐2,2‐diphenyl‐substituted 4‐diazodihydrofuran‐3(2H)‐ones 1a and 1b, respectively, is the Wolff rearrangement, while other photochemical processes, which are giving rise to the formation of CH‐insertion, 1,2‐alkyl‐ or ‐aryl‐shifts, as well as H‐atom‐abstraction products occur to a much lower degree (Schemes 2 and 3). The ratio of similar reaction products from both regioisomers 1a and 1b is essentially independent of their structure, and a substantial effect of the relative position of the Ph and diazo group to each other on the yield of CH‐insertion products does not occur. Based on stereochemical considerations, the Wolff rearrangement of diazodihydrofuran‐3(2H)‐ones apparently proceeds in a concerted manner, whereas the appearance in the reaction mixture of 1,2‐shift and H‐atom‐abstraction products points to the parallel generation during photolysis of singlet and triplet carbenes (Schemes 4 and 5).
Reactivity of 3‐Methylbenzenediazonium Ions with Gallic Acid. Kinetics and Mechanism of the Reaction
Authors: Losada‐Barreiro Sonia , Bravo‐Díaz Carlos 
Published: October 2009

AbstractWe investigated the kinetics and mechanism of the reaction between the 3‐methylbenzenediazonium ions (3MBD), and gallic acids (=3,4,5‐trihydroxybenzoic acid; GA) in aqueous buffer solution under acidic conditions by employing spectrometric, electrochemical, and chromatographic techniques and computational methods. To discern which of the three OH groups of GA is the first one undergoing deprotonation, the geometries of the resulting dianions were optimized by using B3LYP hybrid density‐functional theory (DFT) and a 6‐31G(++d,p) basis set, and the results suggest that the OH group at the 4‐position is the first one which is deprotonated. The variation of the observed rate constant, kobs, with the acidity at a given [GA] follows an upward curve suggesting that the reaction takes place with the dianionic form of gallic acid, GA2−, and rate enhancements of ca. 23000 fold are obtained on going from pH 3.5 up to pH 7.5. At relatively high acidities, the variation of kobs with [GA] is linear with an intercept very close to the value for the thermal decomposition of 3MBD; however, a decrease in the acidity leads to saturation‐kinetics profiles with nonzero, pH‐dependent intercepts. The saturation‐kinetics patterns found suggest the formation of an intermediate in a rapid pre‐equilibrium step, but the nonzero, pH‐dependent intercepts cause the double reciprocal plots of 1/kobs vs. 1/[GA] to curve. This prompts us to propose an alternative reaction mechanism comprising consecutive equilibrium processes involving the bimolecular, reversible formation of a highly unstable (Z)‐diazo ether which undergoes isomerization to the (E)‐isomer through a unimolecular step. The results obtained indicate the complexity of reactions of arenediazonium ions with nucleophilic arenes containing three or more OH groups.
Novel Flavonoids in Dragon's Blood of Daemonorops draco
Authors: Nakashima Ken‐ichi , Abe Naohito , Kamiya Fumiko , Ito Tetsuro , Oyama Masayoshi , Iinuma Munekazu 
Published: October 2009

AbstractThe three novel methylene bis[flavonoids] 1–3, the novel 2‐flavene 4, the new naturally occurring flavan 5, and the new retro‐dihydrochalcone 6 were isolated from dragon's blood of Daemonorops draco, together with seven known compounds. The structures were elucidated by extensive 1D‐ and 2D‐NMR spectroscopic analysis.
Two New Polyoxypregnane Glycosides from Marsdenia tenacissima
Authors: Huang Xue‐Di , Liu Ting , Wang Shu 
Published: October 2009

AbstractTwo new polyoxypregnane glycosides, marsdenosides L and M (1 and 2, resp.), along with five known polyoxypregnane glycosides, 3–7, were isolated from the stem of Marsdenia tenacissima (Roxb.) Wight et Arn. (Asclepiadaceae). The structures and relative configurations of the new compounds were elucidated by spectroscopic methods, including mass spectrometry and NMR spectroscopy.
Juncenolides H – K, New Briarane Diterpenoids from Junceella juncea
Authors: Wang Shih‐Sheng , Chen Yu‐Hui , Chang Jiun‐Yang , Hwang Tsong‐Long , Chen Chung‐Hsiung , Khalil Ashraf Taha , Shen Ya‐Ching 
Published: October 2009

AbstractChemical investigation of the Taiwanese gorgonian coral Junceella juncea resulted in the isolation of four new briarane‐type diterpenoids, juncenolides H, I, J, and K (1–4). Their structures were determined on the basis of spectroscopic analysis, especially 1‐ and 2D‐NMR. The inhibitory effects of compounds 1–4 on superoxide‐anion generation and elastase release by human neutrophils were evaluated.
Irciformonins E – K, C22‐Trinorsesterterpenoids from the Sponge Ircinia formosana
Authors: Shen Ya‐Ching , Shih Pei‐Show , Lin Yun‐Sheng , Lin Yu‐Chi , Kuo Yao‐Haur , Kuo Yuh‐Chi , Khalil Ashraf Taha 
Published: October 2009

AbstractChemical investigation of the sponge Ircinia formosana resulted in the isolation of seven new linear C22‐sesterterpenoids, irciformonins E–K (1–7) in addition to irciformonin A (8), a previously isolated furanosesterterpenoid (=a furan‐moiety‐containing sesterterpenoid) from the same species. The structures were determined by interpretation of HR‐ESI‐MS and 2D‐NMR spectra. The structure of irciformonin A (8) was revised. Compound 5 exhibited significant inhibition of peripheral blood mononuclear cell proliferation induced by phytohemaglutinin.
Verticillane and Norverticillane Diterpenoids from the Formosan Soft Coral Cespitularia hypotentaculata
Authors: Chang Jiun‐Yang , Abd El‐Razek Mohamed H. , Shen Ya‐Ching 
Published: October 2009

AbstractFive new diterpenes, cespihypotins W–Z (1–4, resp.) and cespihypotone (5) have been isolated from the AcOEt‐soluble fraction of the Formosan soft coral Cespitularia hypotentaculata. Two of them having the norverticillane skeleton, i.e., 1 and 2, and the other three, 3–5, possessing a verticillane skeleton. The structures were established as (+)‐(1βH,7E)‐6β,11β‐dihydroxynorverticilla‐4(18),7‐diene‐10,12‐dione (1), (+)‐(1βH,7E)‐6β‐acetoxy‐11β‐hydroxynorverticilla‐4(18),7‐diene‐10,12‐dione (2), (−)‐(1βH,7E)‐6β‐acetoxyverticilla‐4(18),7,11‐triene‐10,12‐γ‐lactone (3), (+)‐(1βH,7E)‐6β‐acetoxy‐10‐hydroxyverticilla‐4(18),7,11‐triene‐10,12‐γ‐lactone (4), and (+)‐(1βH,3Z)‐10β‐hydroxy‐6‐oxoverticilla‐3,11‐diene‐10,12‐γ‐lactone (5), respectively, on the basis of 1D‐ and 2D‐NMR spectroscopic analyses.
Overland flow generation in chaparral ecosystems: temporal and spatial variability
Authors: Valeron B. , Meixner T. 
Published: October 2009

AbstractFire is an important and natural process in the lifecycle of chaparral systems, removing old growth and recycling nutrients. Recent catastrophic wildfires in southern California chaparral have heightened concerns about increased runoff and nutrient export. The goal of this study was to improve understanding of how overland flow is generated in unburned and post‐fire chaparral watersheds. Samples of overland flow were collected from burned and unburned watersheds after rainfall events and multiple regression analysis was used to examine the influence of individual storm characteristics and system moisture on overland flow volume. The results indicate that variation in overland flow generation in the unburned watershed is best explained by storm size, while overland flow in the burned watershed was positively related to storm size and time between storms. These findings suggest that the burned system had decreased infiltration rates and increased soil water repellency. In contrast, there is a statistically significant negative relationship between overland flow 1 year after a fire against different system and precipitation factors revealed a negative correlation with drying period and a positive relationship with rainfall intensity, a combination that suggests reduced repellency. Copyright © 2009 John Wiley & Sons, Ltd.
A comprehensive approach to characterization of the nonlinearity of runoff in the headwaters of the Tarim River, western China
Authors: Xu Jianhua , Li Weihong , Ji Minhe , Lu Feng , Dong Shan 
Published: October 2009

AbstractNonlinear characteristics of the runoff processes in the headwaters of the Tarim River were identified and evaluated using several selected methods, including wavelet analysis, correlation dimension, and R/S analysis. Time‐series of annual data describing runoff, average temperature, and precipitation from 1957 to 2005 were used to construct and test empirical models. The primary findings of this study were as follows: (1) The annual runoff of the headwaters are complex and nonlinear in nature, and they each presented periodic, nonlinear trends at the chosen time scales, chaotic dynamics, and long‐memory characteristics. (2) These nonlinear trends appeared to have resulted from the regional climatic changes that occurred during the study period. The periodicity of changes in runoff occurred on an approximately 25‐year cycle, which appeared to be correlated with temperature and precipitation cycles. In addition, the annual runoff exhibited a significant, positive correlation with the temperature and precipitation factors at the 4‐, 8‐, 16‐, and 32‐year temporal scales. (3) The correlation dimensions of the attractor derived from the runoff time series for the Hotan, Yarkand, and Aksu rivers were all greater than 3·0 and non‐integral, implying that all three rivers are dynamic chaotic systems that are sensitive to initial conditions, and that the dynamic modelling of their annual runoff requires at least four independent variables. (4) The computed Hurst exponents indicate that a long‐term memory characteristic exists in the annual runoff processes. However, there were some differences observed, with the Aksu and Yarkand rivers demonstrating a persistent trait, and the Hotan River exhibiting an anti‐persistent feature. Copyright © 2009 John Wiley & Sons, Ltd.
Multiplex identification of bacteria in bacterial mixtures with surface‐enhanced Raman scattering
Authors: Cam Dilek , Keseroglu Kemal , Kahraman Mehmet , Sahin Fikrettin , Culha Mustafa 
Published: October 2009

AbstractSurface‐enhanced Raman scattering (SERS) is a technique capable of identifying each component in a mixture because of its intrinsically narrow spectral bands. In a clinical setting, the identification of bacteria from its initial culture by collecting the colonies on the culture plate significantly decreases the analysis time and the cost. The identification of bacteria from their mixtures is attempted using SERS. A simple mixing procedure of bacterial samples and concentrated colloidal suspension is proven to be mostly satisfactory for the generation of the reproducible SERS spectra that can be used for bacterial identification. The mixture of three different but related bacterial species Shigella sonnei, Proteus vulgaris, and Erwinia amylovara and three Escherichia coli strains (BFK13, BHK7, DH5 α) are used as model systems to test the feasibility of the approach. The results indicate that it is possible to identify the composition of a bacterial mixture. This approach can easily be utilized for the bacteria originating from the same source with similar growth profiles. Copyright © 2009 John Wiley & Sons, Ltd.
Structural, vibrational spectra and normal coordinate analysis for two tautomers of 4(5)‐(2′‐furyl)‐imidazole
Authors: Ledesma A. E. , Zinczuk J. , López González J. J. , Ben Altabef A. , Brandán S. A. 
Published: October 2009

AbstractWe have synthesized both the 4 and 5 tautomeric forms of 4(5)‐(2′‐furyl)‐imidazole (1) and investigated their molecular vibrations by infrared and Raman spectroscopies as well as by calculation based on the density functional theory (DFT) approach. Examination of the temperature dependence of IR intensity revealed the band characteristics of the 4 and 5 tautomers of (1). Comparison of experimental and calculated chemical shifts in nuclear magnetic resonance (NMR) spectroscopy was made in order to identify the two tautomeric forms. The assignment of vibrational normal modes was performed, and the force field obtained reproduced the experimental vibrational wavenumbers with a root mean‐square deviation (RMSD) value of ca. 13 cm−1 for both tautomers. The natural bond orbital (NBO) study reveals the characteristics of the electronic delocalization of the two tautomeric structures. Copyright © 2009 John Wiley & Sons, Ltd.
Surface‐enhanced Raman spectroscopy coupled with dendritic silver nanosubstrate for detection of restricted antibiotics
Authors: He Lili , Lin Mengshi , Li Hao , Kim Nam‐Jung 
Published: October 2009

AbstractSurface‐enhanced Raman spectroscopy (SERS) coupled with dendritic silver nanosubstrates was used in this study for rapid detection and characterization of restricted antibiotics. Dendritic silver nanosubstrates were prepared through a simple replacement reaction and stored in deionized water for months. SERS methods with near‐IR excitation at 785 nm using silver nanosubstrates were evaluated for detection of three restricted antibiotics (i.e. enrofloxacin, ciprofloxacin, and chloramphenicol) prepared in standard solutions. SERS was capable of identifying and characterizing three antibiotics quickly and accurately. Silver dendrites exhibit satisfactory and consistent performance with an analytical enhancement factor of ∼104. The limit of detection and limit of quantification for antibiotics could reach the level of 20 ppb. Silver dendrites can be kept in deionized water for up to 6 months with no signs of degradation in SERS performance. These results demonstrate a great potential of using SERS coupled with silver dendrites for rapid detection, classification, and quantification of chemical contaminants. Copyright © 2009 John Wiley & Sons, Ltd.
Raman probe to estimate surface energies of embedded semiconductor nanostructures
Authors: Dhara S. , Magudapathy P. , Nair K. G. M. , Raj Baldev 
Published: October 2009

AbstractEmbedded semiconductor nanoclusters (nc‐) of GaN, Si and InN were grown using the ion‐implantation technique and subsequent annealing. Detailed phonon properties were studied for the identification of the grown phases as well as to estimate the stress developed in these embedded structures. The surface energies of the embedded nanoclusters were calculated in analogy with the stressed spherical nanoclusters and excess pressure in a liquid drop. The estimated surface energies for nc‐GaN ∼4 Nm−1, nc‐InN ∼2.7 Nm−1 and nc‐Si ∼1.4 Nm−1 are discussed in the light of possible phase transition in the nanocrystalline systems. Copyright © 2009 John Wiley & Sons, Ltd.
Raman spectroscopy of gallium‐based hydrotalcites of formula Mg6Ga2(CO3)(OH)16· 4H2O
Authors: Frost Ray L. , Palmer Sara J. , Grand Laure‐Marie 
Published: October 2009

AbstractInsight into the unique structure of hydrotalcites has been obtained using Raman spectroscopy. Gallium‐containing hydrotalcites of formula Mg4Ga2(CO3)(OH)12· 4H2O (2:1 Ga‐HT) to Mg8Ga2(CO3)(OH)20· 4H2O (4:1 Ga‐HT) have been successfully synthesized and characterized by X‐ray diffraction and Raman spectroscopy. The d(003) spacing varied from 7.83 Å for the 2:1 hydrotalcite to 8.15 Å for the 3:1 gallium‐containing hydrotalcite. Raman spectroscopy complemented with selected infrared data has been used to characterize the synthesized gallium‐containing hydrotalcites of formula Mg6Ga2(CO3)(OH)16· 4H2O. Raman bands observed at around 1046, 1048 and 1058 cm−1 are attributed to the symmetric stretching modes of the CO32− units. Multiple ν3 CO32− antisymmetric stretching modes are found at around 1346, 1378, 1446, 1464 and 1494 cm−1. The splitting of this mode indicates that the carbonate anion is in a perturbed state. Raman bands observed at 710 and 717 cm−1 assigned to the ν4 (CO32−) modes support the concept of multiple carbonate species in the interlayer. Copyright © 2009 John Wiley & Sons, Ltd.
Influence of inulin/oligofructose on the acid‐induced cold aggregation and gelation of preheated soy proteins
Authors: Tseng Yen‐Chang , Xiong Youling L. , Yang Fuqian 
Published: October 2009

AbstractBACKGROUND: In recent years inulin‐type prebiotics have attracted much attention due to consumers' awareness of the health benefits of functional foods. Currently no information is available about the possible texture‐modifying effect of these non‐ionizable polar carbohydrates in different soy‐based food systems. In this study, the effect of inulin/oligofructose on the cold aggregation and gelation of preheated soy protein isolate (SPI) and its fractions (7S, 11S, and their mixture), induced by glucono‐δ‐lactone (GDL), were evaluated by turbidity (A600) and dynamic rheological measurements.RESULTS: Oligofructose significantly delayed the aggregation of all protein samples and decreased the end‐point optical density of 11S fraction and SPI. Inulin, a long‐chain fructan, only delayed the aggregation of 7S globulin and reduced the capacity of aggregation (A600) of SPI. While oligofructose showed no significant effect, the addition of 5% (w/v) inulin enhanced the gelation of SPI and the 7S/11S mixture, which was demonstrated by the increase in gel storage modulus up to 13.6% and 10.1% (P < 0.05), respectively.CONCLUSION: Inulin was found to enhance the viscoelastic properties of GDL‐induced cold‐set soy protein gels. It is expected that ‘functional’ cold‐set gel products with improved texture can be prepared from preheated soy proteins and inulin. Copyright © 2009 Society of Chemical Industry
Modeling the effects of different mobile phase compositions and temperatures on the retention of various analytes in HPLC
Authors: Jouyban Abolghasem , Soltanpour Shahla , Acree William E. , Thomas Dimitris , Agrafiotou Panagiota , Pappa‐Louisi Adriani 
Published: October 2009

AbstractA mathematical model is proposed for representing the combined effects of mobile phase solvent composition and temperature on the retention of various analytes in HPLC. The applicability of the model in describing the retention of four macrolides in aqueous mixtures of methanol and acetonitrile determined at 20–80°C in various volume fractions of the organic modifiers was shown. The mean percentage deviation (MPD) was computed as an accuracy criterion in which the overall MPD of four analytes investigated in this work was 3.9±1.5% (N=72). The proposed model could be reduced to two simpler versions. The first version concerning the retention data of analytes in one organic modifier at various temperatures produced for the retention description of the above experimental system as well as for the retention of three benzodiazepines in aqueous mixtures of methanol at 25–40°C an overall MPD of 3.6±1.8%. The more reduced version of the model for calculating the retention factor of one analyte in a given organic modifier at various temperatures produced an overall MPD of 1.7±1.1% for both the experimental systems studied. The accuracy of the proposed model is compared with recent models to predict the retention of an analyte with respect to solvent component of the mobile phase and the temperature of column in which the results were comparable. The main advantage of the proposed model is its capability to predict the retention of various analytes considering (i) temperature of the column, (ii) the mobile phase solvent composition, (iii) the chemical structure of the analytes and (iv) the nature of organic modifier.
GC separation of amino acid enantiomers via derivatization with heptafluorobutyl chloroformate and Chirasil‐L‐Val column
Authors: Zahradníčková Helena , Hušek Petr , Šimek Petr 
Published: October 2009

AbstractHeptafluorobutyl chloroformate (HFBCF), a recently introduced derivatization reagent, was examined in enantioseparation of amino acids (AAs) by GC. Twenty proteinogenic AAs, plus ornithine, cystine and 4‐fluorophenylalanine (internal standard) were treated with the reagent and separation properties of the derivatives were assessed on a Chirasil‐Val capillary column. Nineteen AA enantiomers were efficiently separated in 43 min except proline, arginine and cystine. The HFBCF derivatives of the studiedDL‐AAs show improved separation over other chloroformate‐based derivatives hitherto reported. A combination of the improved and faster separation with a simple derivatization protocol, involving an immediate one‐step reaction–extraction in two‐phase aqueous‐organic medium, and low elution temperatures extend application of HFBCF to chiral AA analysis.
Fabrication of Complex Micelles with Tunable Shell for Application in Controlled Drug Release
Authors: Wu Chenglin , Ma Rujiang , He Huan , Zhao Lizhi , Gao Hongjun , An Yingli , Shi Linqi 
Published: October 2009

AbstractAt room temperature, diblock copolymers of PLA‐b‐PNIPAM and PEG‐b‐PLA self‐assembled into complex micelles with a PLA core and a mixed PEG/PNIPAM shell. By increasing the temperature, these complex micelles could be converted into a core‐shell‐corona structure composed of a PLA core, a collapsed PNIPAM shell and a soluble PEG corona, and the PEG chains stretched from the inner core to outside, leading to the formation of PEG channels. The PEG channels could be used for the exchange of substance between the core and the external environment. Compared with core‐shell micelles, complex micelles with a core‐shell‐corona structure could avoid the burst diffusion in the release of ibuprofen and inhibit the degradation of PLA by lipase to a certain extent.magnified image
Mark–Houwink Parameters for the Universal Calibration of Acrylate, Methacrylate and Vinyl Acetate Polymers Determined by Online Size‐Exclusion Chromatography—Mass Spectrometry
Authors: Gruendling Till , Junkers Tanja , Guilhaus Michael , Barner‐Kowollik Christopher 
Published: October 2009

AbstractSize exclusion chromatography coupled online to electrospray ionization mass spectrometry (SEC/ESI‐MS) is employed to establish universal calibration (UC) relationships for a number of linear poly(alkyl acrylates) and poly(alkyl methacrylates) as well as poly(vinyl acetate) synthesized via radical chain transfer polymerization. It is demonstrated that in the analyzed molecular weight range, Mark–Houwink–Kuhn–Sakurada (MHKS) coefficients can be successfully determined in relation to values of pMMA. The agreement between the UC model using mass spectrometry‐derived MHKS coefficients and the measured data was generally better than 10%. The MHKS values reported herein are expected to remain valid up to 20 kDa. A comparison with the outcome of UC using literature reported MHKS coefficients determined by intrinsic viscosity—molecular weight (IV‐MW) measurements is provided. Errors of more than 30% can result when these literature values are employed in the low molecular weight range ( < 20 kDa). Use of MHKS coefficients derived from IV‐MW measurements in UC is, therefore, strongly discouraged at molecular weights below 20 kDa.magnified image