An easy access to a 3,6-branched mannopentaoside bearing one terminal [1-<Superscript>13</Superscript>C]-labeled <Emphasis Type="SmallCaps">D</Emphasis>-mannopyranose residue

Methyl 2,4-di-O-benzoyl-α-D-mannopyranoside was used as a key intermediate in the synthesis of 3,6-branched mannopentaoside bearing one terminal D-[1-¹³C]mannopyranose residue, viz., methyl 6-O-[3,6-di-O-(α-D-mannopyranosyl)-α-D-mannopyranosyl)-3-O-{α -D-[1-¹³C]mannopyranosyl}-α-D-mannopyranoside. Dedicated to Academician N. K. Kochetkov on the occasion of his 90th birthday. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1250–1255, May, 2005.     

Polysaccharides from Fabaceae. IV. Galactomannan from <Emphasis Type="Italic">Gueldenstaedtia monophylla</Emphasis> seeds

Galactomannan (yield 1.73% of seed mass) with molecular weight 808 kDa was isolated from seeds of Gueldenstaedtia monophylla Fisch. (Fabaceae). Its solutions were typically highly viscous with [η] 664.7 mL/g and optically active with [α]_D +45.2°. It consisted of galactose and mannose in a 1:1.91 ratio. Physical chemical methods established that the principal chain of the polysaccharide consisted of 1,4-β-D-mannopyranose units substituted 50.1% in the C-6-position by single α-D-galactopyranose units and traces of 6-O-α-galactopyranosylgalactopyranose. The contents of mannobiose blocks substituted by galactose Man–Man, (Gal)Man–Man/Man–Man(Gal), and (Gal)Man–Man(Gal) in the galactomannan macromolecule were 23, 42, and 35%, respectively.     

Phytoecdysteroids of plants of theSilene genus. XIX. The structure of sileneoside G

The phytoecdysteroid sileneoside G has been isolated from the roots ofSilene brahuica Boiss., and its structure has been established on the basis of chemical transformations and spectral, characteristics as ecdysterone 3-O-α-D-galactopyranoside 22-O-α-D-glucopyranoside. Enzymatic hydrolysis yielded ecdysterone and sileneoside D. Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (371) 120 64 75. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 663–665, September–October, 1998.     

Thermal transitions and fat droplet stability in ice-cream mixmodel systems

We studied thermal transitions and physical stability of oil-in-water emulsions containing different milk fat compositions, arising from anhydrous milk fat alone (AMF) or in mixture (2:1 mass ratio) with a high melting temperature (AMF–HMT) or a low melting temperature (AMF–LMT) fraction. Changes in thermal transitions in bulk fat and emulsion samples were monitored by differential scanning calorimetry (DSC) under controlled cooling and reheating cycles performed between 50 and –45°C (5°C min^–1). Comparison between bulk fat samples and emulsions indicated similar values of melting completion temperature, whereas initial temperature of fat crystallization (T_onset) seemed to be differently affected by storage temperature depending on triacylglycerols (TAG) composition. After storage at 4°C, T_onset values were very similar for emulsified and non-emulsified AMF–HMT blend, whereas they were lower (by approx. 6°C) for emulsions containing AMF or mixture of AMF–LMT fraction. After storage at –30°C, T_onset values of re-crystallization were higher in emulsion samples than in bulk fat blends, whatever the TAG fat composition. Light scattering measurements and fluorescence microscopic observations indicated differences in fat droplet aggregation-coalescence under freeze-thaw procedure, depending on emulsion fat composition. It appeared that under quiescent freezing, emulsion containing AMF–LMT fraction was much less resistant to fat droplet aggregation-coalescence than emulsions containing AMF or AMF–HMT fraction. Our results indicated the role of fat droplet liquid-solid content on emulsion stability.     

Triterpene glycosides ofTragacantha and their genins. Cyclostipulosides A and B fromTragacantha stipulosa

Two new triterpene glycosides of the cycloartane series, which have been called cyclostipulosides A and B, have been isolated in the individual form from the roots ofTragacantha stipulosa Boviss. Their structures have been established by physicochemical methods. Cyclostipuloside A is 24R-cycloartane-3β,6α,16β,24,25-pentaol 16-O-β-D-glucopyranoside 3-O-β-D-xylopyranoside, and cyclostipuloside B is 24R-cycloartane-3β,6α,16β,24,25-pentaol 6-O-α-L-arabinopyranoside 16-O-β-D-glucopyranoside 3-O-β-D-xylopyranoside. By the acid hydrolysis of cyclostipulosides A and B we have obtained the new glycoside 24R-cycloartane-3β,6α,16β,24,25-pentaol 16-O-β-D-glucopyranoside. Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (371) 120 64 75. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 670–674, September–October, 1998.     

Triterpene glycosides ofHedera canariensis III. Determination of the structures of glycosides L-F1, L-F2, and L-I2 from the leaves of Algerian ivy

The leaves of Algerian ivyHedera canariensis Willd. (Araliaceae) have yielded two new triterpene glycosides — caulophyllogenin 3-O-α-L-rhamnopyranosyl-(1→2)-O-α-L-arabinopyranoside (L-F₂) and its 28-O-α-L-rhamnopyranosyl-(1→4)-O-β-D-gentiobiosyl ester (L-I₂) - and also the previously known hederagenin 3-O-α-L-rhamnopyranosyl-(1→2)-O-β-D-glucopyranoside (L-F₁). The structures of the glycosides were established on the basis of chemical transformations and¹H and¹³C NMR spectroscopy. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 777–781, November–December, 1998.     

Stereospecific mannosylations of myo -inasitol: Synthesis of manno- myo -inositol fragment of Mycobacterium tuberculosis

Methyl iodide activated stereospecific α-mannosylations utilising 2-pyridyl-1-thiomannopyranoside derivatives (2,3,4) as donors and suitably protected myo-inositol derivatives (1,25,27,29) as acceptors to prepare 2-0-α-D-mannopyranosyl-6-[O-α-D-mannopyranosyl-(1–6)-O-α-D-mannopyranosyl-(l-6)-O-α-D-mannopyranosyl]-D-myo-inositol derivative (31) is described. IICT Commun. No. 3355     

Polysaccharides of Fabaceae. VI. Galactomannans from seeds of <Emphasis Type="Italic">Astragalus alpinus</Emphasis> and <Emphasis Type="Italic">A. tibetanus</Emphasis>

Galactomannans with galactose:mannose ratios 1:1.48 and 1:1.33, [α]_D +67.9 and +76.4°, [η] 870.3 and 1337.1 mL/g, and molecular weights 999 and 1549 kDa, respectively, were isolated in 0.59 and 4.65% yields (of seed mass) from seeds of Astragalus alpinus and A. tibetanus (Fabaceae). Physicochemical methods (CrO₃ oxidation; methylation–GC/MS; IR, NMR, and ¹³C spectroscopy) found that the main polysaccharide chain consisted of 1,4-β-D-mannopyranose units substituted 67.5% (A. alpinus) and 75.2% (A. tibetanus) at the C-6 position by single α -D-galactopyranose units. The contents of mannobiose blocks Man–Man, (Gal)Man–Man/Man–Man(Gal), and (Gal)Man–Man(Gal) variously substituted with galactose were according to ¹³C NMR spectroscopy 15.9, 55.5, and 28.6% in A. alpinus galactomannan and 9.9, 42.3, and 47.8% in A. tibetanus galactomannan.     

Triterpene glycosides ofHedera canariensis II. Determination of the structures of glycosides L-E2 and L-H3 from the leaves of Algerian ivy

The structures of two new triterpene glycosides, L-E₂ and L-H₃ from the leaves of Algerian ivyHedera canariensis Willd. (fam. Araliaceae), have been established on the basis of chemical and spectral characteristics: they are 30-norhederagenin 3-O-α-L-rhamnopyranosyl-(1→2)-O-α-L-arabinopyranoside and the 28-O-α-L-rhamnopyranosyl-(1→4)-O-β-D-gentiobiosyl ester of 30-norhederagenin 3-O-α-L-rhamnopyranosyl-(1→2)-O-α-L-arabinopyranoside, respectively. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 772–776, November–December, 1998.     

Separation, purification and structure elucidation of a polysaccharide from root of Cudrania tricuspidata

A water-soluble polysaccharide (CPS-0) was obtained from the root of Cudrania tricuspidata (Carr.) Bur., by hot water extraction (70°C), deproteination using enzymolysis and Sevag method, precipitation with ethanol, and fractionation through DEAE-Sephadex A-50 chromatography. The purity of CPS-0 was determined by HPLC and the structure was elucidated by monosaccharide composition analysis, methylation analysis, GC, GC-MS, NMR spectral (¹H-NMR, ¹³C-NMR, HMQC), UV, IR, and elemental analysis. The CPS-0 was found to contain glucose residues only. The average repeating unit is a decasaccharide having a backbone consisting of 1,4-linked α-D-glucopyranosyl residues to which the side chain consisting of terminal and 1,4-linked α-D-glucopyranosyl residues was attached at position 6 of the branching residues. __________ Translated from Chemical Journal of Chinese Universities, 2007, 28(6): 1088–1091 [译自: 高等学校化学学报]     

Thermal properties of isomalt: A diastereomer mixture

Isomalt, a commercial sugar alcohol widely used as a sweetener, is approximately a 1:1 mixture of two diastereomers, -D-glucopyranosyl-1-6-mannitol (GPM) and -D-glucopyranosyl-1-6-sorbitol (GPS). A calorimetric investigation has been carried out on mixtures of isomalt with GPS, in the (molar) composition range 0.45<x_GPS<1, for both crystalline and amorphous states.The GPS-rich portion of the solid-liquid GPM/GPS phase diagram was established and discussed in light of the existing literature. New evidence was given for the non-ideality of GPM/GPS mixtures, by indicating excess interactions in the melt and/or in the solid state. The commonly accepted hypothesis of a simple GPM/GPS eutectic forming isomalt was refuted in favour of more complicated mixture behaviour with possible formation of a complex.Glass transition and physical ageing of isomalt and GPS were re-visited, with peculiar attention given to the measurement conditions. Standard thermal histories were adapted to each sample and the fictive temperature was used for the characterisation of the structural glass states. A linear increase of the fictive temperature was found upon passing from pure GPS to x_GPS=0.45. GPS showed a slightly higher enthalpy relaxation rate than isomalt.This revised version was published online in November 2005 with corrections to the Cover Date.     

Melting behavior of poly(oxytetramethylene)-<Emphasis Type="Italic">alt</Emphasis>-(aromatic oligoamide) block copolymers

Using temperature-modulated differential scanning calorimetry, the melting behaviour of poly(oxytetramethylene)-alt-(aromatic oligoamide) (POTM-alt-AOA) has been studied in comparison with that of polyoxytetramethylene glycohols (POTMGs). The apparent melting temperature of the block copolymers is found to be less than that of the corresponding POTMGs by approximately 30°C. The relaxation time of melting of a POTM segment has been estimated and compared with that of POTMG. The relaxation time of POTM-alt-AOA is slightly shorter than that of POTMG when the molar mass of the POTM segment is 2900; however, it is longer when the molar mass is 1400.     

Polysaccharides of Fabaceae. I. Galactomannan of Astragalus sericeocanus seeds

Galactomannan (yield 3.58% of seed mass) of molecular weight 876 kDa was isolated from seeds of Astragalus sericeocanus Gontsch. (Fabaceae). Its solutions had high viscosity [η], 764.6 mL/g, and optical density [α]_D +65.3°. The polysaccharide consisted of galactose and mannose in molar ratio 1:1.58. The main chain of the galactomannan macromolecule was constructed of 1,4-β-D-mannopyranose units, 63% of which were substituted at C-6 by single α-D-galactopyranose units. ¹³C NMR spectroscopy established that the galactomannan contained units of differently substituted galactose mannobiose units: Man-Man, (Gal)Man-Man, and/or Man-Man(Gal) in addition to (Gal)Man-Man(Gal), the ratio of which was 0.15:0.51:0.34. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 555–557, November–December, 2008.     

Fabaceae Polysaccharides. III. Galactomannan from <Emphasis Type="Italic">Astragalus cicer</Emphasis> seeds

Seeds of Astragalus cicer L. (Fabaceae) afforded a galactomannan (5.90% yield of seed mass) of molecular weight 1064 kDa, solutions of which had high viscosity [η] 925.5 mL/g and optical activity [α]_D +71.9°. The galactomannan consisted of galactose and mannose units in a 1:1.39 ratio. Physicochemical methods established that the main chain of the polysaccharide consisted of 1,4-β-D-mannopyranose units substituted at 72% of the C-6 positions by single α-D-galactopyranose units. The content of variously substituted galactose mannobiose units Man–Man, (Gal)Man–Man/Man–Man(Gal) and (Gal)Man–Man(Gal) in the galactomannan were 18.7, 19.8, and 61.5%, respectively.     

Thermal decomposition of two synthetic glycosides by TG,DSC and simultaneous Py-GC-MS analysis

To develop thermal stable flavor, two glycosidic bound flavor precursors, geranyl-tetraacetyl-β-D-glucopyranoside (GLY-A) and geranyl-β-D-glucopyranoside (GLY-B) were synthesized by the modified Koenigs–Knorr reaction. The thermal decomposition process and pyrolysis products of the two glycosides were extensively investigated by thermogravimetry (TG), differential scanning calorimeter (DSC) and on-line pyrolysis-gas chromatography mass spectroscopy (Py-GC-MS). TG showed the T _p of GLY-A and GLY-B were 254.6 and 275.7°C. The T _peak of GLY-A and GLY-B measured by DSC were 254.8 and 262.1°C respectively. Py-GC-MS was used for the simply qualitative analysis of the pyrolysis products at 300 and 400°C. The results indicated that: 1) A large amount of geraniol and few by-products were produced at 300°C, the by-products were significantly increased at 400°C; 2) The characteristic pyrolysis product was geraniol; 3) The primary decomposition reaction was the cleavage of O-glycosidic bound of the two glycosides flavor precursors. The study on the thermal behavior and pyrolysis products of the two glycosides showed that this kind of flavor precursors could be used for providing the foodstuff with specific flavor during heating process.     

Dilectric and thermal properties of PEO doped with cadimium chloride salt

The main aim of this research is to investigate the effect of salt concentration on the dielectric properties(AC (σ_AC),permittivity（ε′）,dielectric loss（ε″）,and dielectric relaxation process) and melting behavior of polyethylene oxide （PEO）/CdCl₂ complexes.The dielectric study was carried out over a frequency range 10-335 kHz and a temperature range 25-45℃.The AC conductivity,permittivity and dielectric loss of the PEO/CdCl₂ complexes increase with increasing salt concentration and temperature.Also,it was found that the addition of CdCl₂ salt to PEO host reduced the melting temperature of PEO host.Dielectric results reveal that the relaxation process of these complexes is due to viscoelastic relaxation or non-Debye relaxation at room temperature.Additionally,it was found that relaxation behavior remained viscoelastic at different temperatures and salt concentrations.     

Preparation and characterization of fused-silica capillary columns coated with <Emphasis Type="Italic">m</Emphasis>-carborane–siloxane copolymers for gas chromatography

The carborane–siloxane copolymers Dexsil 300, a 34.5% bis(dimethylsilyl)-m-carborane–65.5% dimethylsiloxane copolymer, and Dexsil 400, a 24.9% bis(dimethylsilyl)-m-carborane–50.8% dimethyl, 24.3% methylphenylsiloxane copolymer, were coated on fused silica capillary columns and their gas chromatographic properties were evaluated. Their selectivity was evaluated using both Rohrschneider–McReynolds constants and triacylglycerol indices. The bis(dimethylsilyl)-m-carborane unit turned out to be equivalent to two dimethylsiloxy units and one half of a diphenylsiloxy unit. The m-carborane unit was found to cause a 15–25 K shift in the elution temperature between 120 and 360 °C. The working range was from 20 and 0 °C to 380 °C for Dexsil 300 and Dexsil 400, respectively. The column bleeding levels at 380 °C were below 20 and 15 pA for Dexsil 300 and Dexsil 400, respectively.     

Thermal stability of recombinant green fluorescent protein (GFPuv) at various pH values

The thermal stability of the recombinant green fluorescent protein (GFPuv) expressed by Escherichia coli cells and isolated by three-phase partitioning extraction with hydrophobic interaction chromatography was studied. The GFPuv (3.5–9.0 μg of GFPuv/mL) was exposed to various pH conditions (4.91–9.03) and temperatures (75–95°C) in the 10 mM buffers: acetate (pH 5.0–7.0), phosphate (pH 5.5–8.0), and Tris-HCl (pH 7.0–9.0). The extent of protein denaturation (loss of fluorescence intensity) was expressed in decimal reduction time (D-value), the time exposure required to reduce 90% of the initial fluorescence intensity of GFPuv. For pH 7.0 to 8.0, the thermostability of GFPuv was slightly greater in phosphate buffer than in Tris-HCl. At 85°C, the D-values (pH 7.1–7.5) ranged from 7.24 (Tris-HCl) to 13.88 min (phosphate) The stability of GFPuv in Tris-HCl (pH>8.0) was constant at 90 and 95°C, and the D-values were 7.93 (pH 8.38–8.92) and 6.0 min (pH 8.05–8.97), respectively. The thermostability of GFPuv provides the basis for its potential utility as a fluorescent biologic indicator to assay the efficacy of moist-heat treatments at temperatures lower than 100°C.     

New triterpene glycoside from <Emphasis Type="Italic">Cyclamen adzharicum</Emphasis> tubers

Nine pure glycosides were isolated from total saponins of Cyclamen adzharicum Pobed. (Primulaceae). The total chemical structure of cyclamen F, 3β-O-[β-D-Xylp(1→2)]-[β-D-Glcp(1→2)]-(β-D-Glcp(1→4)-α-L-Arap)-16α-hydroxy-13,28-epoxy-30,30-dibutoxyolean, was elucidated using modern physicochemical and spectral methods (NMR, ¹H, ¹³C, HMBC, HMQC, DEPT, COSY, MS). A glycoside with the cyclamen F chemical structure has not been reported and, therefore, is a new organic compound.     

Stability and physical structure tests of piperidyl and morpholinyl derivatives of diphenyl-diketo-pyrrolopyrroles (DPP)

Crystalline structure, thermo-oxidative and thermal stability of symmetrical and asymmetrical piperidyl and morpholinyl derivatives of both N-substituted and non-N-substituted butyl diphenyl-diketo-pyrrolopyrrole (DPP) pigments were studied using differential scanning calorimetry (DSC) and thermogravimetry (TG). Except for the asymmetrical morpholine DPP derivative, all the samples showed melting peaks which were relatively close to their degradation temperatures (from 260 to 430 °C). Using DSC, monotropic polymorphism was revealed in the symmetrical piperidyl-N-butyl-derivative which confirmed earlier observation about tendency of symmetrical N-alkyl DPP derivates to form several crystalline structures. TG carried out under nitrogen atmosphere served for distinguishing of evaporation/sublimation and degradation temperatures. Temperatures of evaporation/sublimation were typically 10–30 °C lower in comparison with temperatures of thermal degradation. The highest thermal (450 °C) and thermo-oxidative stability (around 360 °C) showed the DPP derivatives containing morpholine moieties with no alkyl substitution on NH-group of DPP core. The presence of the latter was found to be the most destabilizing factor. Piperidyl group showed more stabilizing effect due to its polar character and its influence on π–π intermolecular interactions of neighbouring phenyl groups. The highest stabilizing effect of morpholine moiety on DPP structure was explained based on the presence of polar oxygen atom in that group. The preparations of 3,6-di-(4-morpholinophenyl)-2,5-dihydro-pyrrolo[3,4-c]pyrrole-1,4-dione and 3-(phenyl)-6-(4-morpholinophenyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione are reported.