Structure of the O-polysaccharides of the lipopolysaccharides of Mesorhizobium loti HAMBI 1148 and Mesorhizobium amorphae ATCC 19655 containing two O-methylated monosaccharides

The O-polysaccharide of Mesorhizobium loti HAMBI 1148 was obtained by mild acid degradation of the lipopolysaccharide and studied by sugar and methylation analyses, Smith degradation, and ¹H and ¹³C NMR spectroscopies, including 2D ¹H/¹H COSY, TOCSY, ROESY, and H-detected ¹H/¹³C HSQC experiments. The O-polysaccharide was found to have a branched hexasaccharide-repeating unit of the following structure:where 2-acetamido-2-deoxy-4-O-methyl-d-glucose (d-GlcNAc4Me) and methyl group on 2-substituted d-rhamnose (Me) shown in italics are present in ∼80% and ∼40% repeating units, respectively. Similar studies of the O-polysaccharide from Mesorhizobium amorphae ATCC 19655 by sugar analysis and NMR spectroscopy revealed essentially the same structure but a higher content of 3-O-methyl-d-rhamnose (∼70%).     

Structure of the O-polysaccharide from the lipopolysaccharide of Providencia alcalifaciens O31 containing an ether of d-mannose with (2R,4R)-2,4-dihydroxypentanoic acid

Recently, ether-linked diastereomeric 2,4-dihydroxypentanoic acids have been reported as new components of bacterial glycans [Shashkov, A. S. et al.Nat. Prod. Commun.2008, 3, 1625-1630]. In this work, an ether of (2R,4R)-2,4-dihydroxypentanoic acid (Dhpa) with d-mannose was identified in the O-polysaccharide of Providencia alcalifaciens O31, and the polysaccharide structure was elucidated. Studies by NMR spectroscopy confirmed the ether linkage between O-2 of Dhpa and O-4 of Man, and the absolute configuration of Man was determined after ether cleavage with boron trichloride. In the polysaccharide, Dhpa was found to exist partially in the form of 1,4-lactone. Using sugar and methylation analyses along with ¹H and ¹³C NMR spectroscopy, including 2D ¹H,¹H COSY, TOCSY, ROESY, H-detected ¹H,¹³C HSQC, and gHMBC experiments, the following structure of the tetrasaccharide repeating unit of the polysaccharide was established:     

Synthesis and characterization of platinum(IV) complexes with N,S and S,S heterocyclic ligands

The reactions of [PtMe₃(OAc)(bpy)] (4) with the N,S and S,S containing heterocycles, pyrimidine-2-thione (pymtH), pyridine-2-thione (pytH), thiazoline-2-thione (tztH) and thiophene-2-thiol (tptH), resulted in the formation of the monomeric complexes [PtMe₃(-κS)(bpy)] ( = pymt, 5; pyt, 6; tzt, 7; tpt, 8), where the heterocyclic ligand is coordinated via the exocyclic sulfur atom. In contrast, in the reactions of [PtMe₃(OAc)(Me₂CO)_x] (3, x = 1 or 2) with pymtH, pytH, tztH and tptH dimeric complexes [{PtMe₃(μ-)}₂] (μ- = pymt, 9; pyt, 10; tzt, 11) and the tetrameric complex [{PtMe₃(μ₃-tpt-κS)}₄] (12), respectively, were formed. The complexes were characterized by microanalyses, ¹H and ¹³C NMR spectroscopy and negative ESI-MS (12) measurements. Single-crystal X-ray diffraction analysis of [PtMe₃(pymt-κS)(bpy)] (5) exhibited a conformation where the pymt ligand lies nearly perpendicular to the complex plane above the bpy ligand that was also confirmed by quantum chemical calculations on the DFT level of theory.     

Isolation and characterization of a heteropolysaccharide from the corm of Amorphophallus campanulatus

A water-soluble polysaccharide isolated from the aqueous extract of the corm of Amorphophallus campanulatus was found to contain d-galactose, d-glucose, 4-O-acyl-d-methyl galacturonate, and l-arabinose in a molar ratio 2:1:1:1. Structural investigation of the polysaccharide was carried out using acid hydrolysis, methylation analysis, periodate oxidation study, and NMR studies (¹H, ¹³C, DQF-COSY, TOCSY, NOESY, ROESY, HMQC, and HMBC). On the basis of the above-mentioned experiments the structure of the repeating unit of the polysaccharide was established as:This molecule showed splenocyte activation.     

Structure of the O-polysaccharide from the lipopolysaccharide of Providencia alcalifaciens O12

The O-polysaccharide was obtained by mild acid degradation of the lipopolysaccharide of Providencia alcalifaciens O12. Its structure was studied by sugar analysis using GLC of the alditol acetates and (S)-2-octyl glycosides, methylation analysis, Smith degradation, and ¹H and ¹³C NMR spectroscopy, including 2D ¹H-¹H COSY, TOCSY, ROESY, ¹H-¹³C HSQC, and HMBC experiments. It was found that the polymer is a neutral heteropolysaccharide and has a branched heptasaccharide repeating unit with the following structure:     

Structural characterization of a heteropolysaccharide isolated from hot water extract of the stems of Amaranthus tricolor Linn. (Amaranthus gangeticus L.)

A water-soluble polysaccharide (PS-I), isolated from the aqueous extract of the stems of Amaranthus tricolor Linn. (Amaranthus gangeticus L.), was found to consist of l-arabinose, methyl-d-galacturonate, d-galactose, and 3-O-Ac-l-rhamnose in a molar ratio of nearly 1:1:1:1. On the basis of total acid hydrolysis, methylation analysis, periodate oxidation, and NMR studies (¹H, ¹³C, TOCSY, DQF-COSY, NOESY, ROESY, HMQC, and HMBC), the structure of the repeating unit of the PS-I is determined as:     

Structure of the O-antigen of Yersinia pseudotuberculosis O:4a revised

The O-specific polysaccharide was isolated by mild acid degradation of the lipopolysaccharide of Yersinia pseudotuberculosis O:4a and studied by NMR spectroscopy, including 2D ROESY and ¹H, ¹³C HMBC experiments. The following structure of the pentasaccharide repeating unit of the polysaccharide was established, which differs from the structure reported earlier [Gorshkova, R. P. et al., Bioorg. Khim. 1983, 9, 1401-1407] in the linkage modes between the monosaccharides: where Tyv stands for 3,6-dideoxy-d-arabino-hexose (tyvelose). The structure of the Y. pseudotuberculosis O:4a antigen resembles that of Y. pseudotuberculosis O:2c, which differs in the presence of abequose (3,6-dideoxy-d-xylo-hexose) in place of tyvelose only.     

Structure of a polysaccharide from the lipopolysaccharides of Vibrio vulnificus strains CECT 5198 and S3-I2-36, which is remarkably similar to the O-polysaccharide of Pseudoalteromonas rubra ATCC 29570

High-molecular-mass polysaccharides were released by mild acid degradation of the lipopolysaccharides of two wild-type Vibrio vulnificus strain, a flagellated motile strain CECT 5198 and a non-flagellated non-motile strain S3-I2-36. Studies by sugar analysis and partial acid hydrolysis along with ¹H and ¹³C NMR spectroscopies showed that the polysaccharides from both strains have the same trisaccharide repeating unit of the following structure:→4)-β-d-GlcpNAc3NAcylAN-(1→4)-α-l-GalpNAmA-(1→3)-α-d-QuipNAc-(1→where QuiNAc stands for 2-acetamido-2,6-dideoxyglucose, GalNAmA for 2-acetimidoylamino-2-deoxygalacturonic acid, GlcNAc3NAcylAN for 2-acetamido-3-acylamino-2,3-dideoxyglucuronamide and acyl for 4-d-malyl (∼30%) or 2-O-acetyl-4-d-malyl (∼70%). The structure of the polysaccharide studied resembles much that of a marine bacterium Pseudoalteromonas rubra ATCC 29570 reinvestigated in this work. The latter differs in (i) the absolute configuration of malic acid (l vs d), (ii) 3-O-acetylation of GalNAmA and (iii) replacement of QuiNAc with its 4-keto biosynthetic precursor.     

Structures of the O-antigens of Escherichia coli O13, O129, and O135 related to the O-antigens of Shigella flexneri

O-Polysaccharides (O-antigens) were isolated from Escherichia coli O13, O129, and O135 and studied by chemical analyses along with 2D ¹H and ¹³C NMR spectroscopy. They were found to possess a common →2)-l-Rha-(α1→2)-l-Rha-(α1→3)-l-Rha-(α1→3)-d-GlcNAc-(β1→ backbone, which is a characteristic structural motif of the O-polysaccharides of Shigella flexneri types 1-5. In both the bacterial species, the backbone is decorated with lateral glucose residues or/and O-acetyl groups. In E. coli O13, a new site of glycosylation on 3-substituted Rha was revealed and the following O-polysaccharide structure was established:The structure of the E. coli O129 antigen was found to be identical to the O-antigen structure of S. flexneri type 5a specified in this work and that of E. coli O135 to S. flexneri type 4b reported earlier.     

The structure of the O-antigen in the endotoxin of the emerging food pathogen Cronobacter (Enterobacter) muytjensii strain 3270

Strains of the Gram-negative bacterium Cronobacter (formerly known as Enterobacter) sakazakii have been identified as emerging opportunistic pathogens that can cause enterocolitis, bacteraemia, meningitis, and brain abscess, and they have been particularly associated with meningitis in neonates where infant milk formulae have been epidemiologically linked to the disease. A study of the lipopolysaccharides produced by clinical isolates using chemical, 2D ¹H and ¹³C NMR, and MS methods revealed that the O-polysaccharide produced by Cronobactermuytjensii strain 3270, isolated from powdered infant formula from Denmark, was a linear unbranched polymer of a repeating pentasaccharide unit composed of 2-acetamido-2-deoxy-d-galactose (d-GalNAc), 2-acetamido-2-deoxy-d-glucose (d-GlcNAc), 3-acetamido-3-deoxy-d-quinovose (d-Qui3NAc), l-rhamnose (l-Rha), and d-glucuronic acid (d-GlcA) in equimolar ratio, and has the structureThe specific structural characteristics of the O-polysaccharides of C.muytjensii may be of value in the identification and tracking of the bacterial pathogen.     

Glucogalactan: A polysaccharide isolated from the cell-wall of Verticillium Lecanii

A water-soluble polysaccharide was extracted with alkali from the cell wall of Verticillium lecanii (also called Lecanicillium lecanii). After freezing and thawing, the water-soluble fraction was purified by gel filtration chromatography on Sepharose CL-6B and eluted as one peak by HPSEC/RID. Monosaccharide analysis showed galactose and glucose (1.1:1), with traces of mannose (<1%). The structural characteristics were determined by spectroscopic analysis, FT-IR and 1D and 2D ¹H and ¹³C NMR, and methylation results. On the basis of the data obtained, the following structure of the polysaccharide (E₃S_IV fraction) was established:     

Structure of the O-polysaccharide of Cronobacter sakazakii O2 with a randomly O-acetylated l-rhamnose residue

Studies by sugar analysis and partial acid hydrolysis along with one- and two-dimensional ¹H and ¹³C NMR spectroscopy and high-resolution ESI MS showed that the O-polysaccharide (O-antigen) Cronobacter sakazakii ATCC 29004 (serotype O2) possesses a branched hexasaccharide O-unit with a randomly mono-O-acetylated terminal rhamnose residue in the side chain and the following structure:A similar structure has been reported for the O-polysaccharide of C. sakazakii 767, which differs in the presence of an additional lateral α-d-Glcp residue on GlcNAc and the pattern of O-acetylation (Czerwicka, M., Forsythe, S. J.; Bychowska, A.; Dziadziuszko, H.; Kunikowska, D.; Stepnowski, P.; Kaczynski, Z. Carbohydr. Res.2010, 345, 908-913).     

Glucans from the alkaline extract of an edible mushroom, Pleurotus florida, cv Assam Florida: isolation, purification, and characterization

Three different glucans (PS-I, PS-II, and PS-III) were isolated from the alkaline extract of the fruiting bodies of an edible mushroom Pleurotus florida, cultivar Assam Florida. On the basis of total acid hydrolysis, methylation analysis, periodate oxidation, Smith degradation, and NMR experiments (¹H, ¹³C, DEPT-135, DQF-COSY, TOCSY, NOESY, ROESY, HMQC, and HMBC), the structure of the repeating unit of these polysaccharides was established as follows:     

A (1→6)-β-glucan from a somatic hybrid of Pleurotus florida and Volvariella volvacea: isolation, characterization, and study of immunoenhancing properties

A water-soluble immunoenhancing polysaccharide was isolated from the aqueous extract of fruit bodies of somatic hybrid (Pflo Vv5 FB), obtained through protoplast fusion between Pleurotus florida and Volvariella volvacea strains. On the basis of acid hydrolysis, the polysaccharide was found to contain glucose only. Methylation analysis, periodate oxidation along with ¹H, DEPT-135, and ¹³C NMR spectroscopy, including two-dimensional TOCSY, DQF-COSY, NOESY, ROESY, 1H,13C-HMQC, and HMBC experiments showed that the polysaccharide was a (1→6)-β-d-glucan, which was not a constituent of any of the parent mushrooms previously reported.This glucan stimulated the macrophages, splenocytes, and thymocytes.     

(25S)-Cholesten-26-oic acid derivatives from an Indonesian soft coral Minabea sp.

(25S)-3-Oxocholesta-1,4-dien-26-oic acid (1) and a new (25S)-18-acetoxy-3-oxocholesta-1,4-dien-26-oic acid (2) were isolated from a soft coral Minabea sp. (cf. aldersladei) collected in North Sulawesi, Indonesia, together with two known cholic-acid-type compounds, 3-oxochol-1,4-dien-24-oic acid (3) and 3-oxochol-4-en-24-oic acid (4). The structures of these compounds were determined on the basis of their spectroscopic data. The absolute stereochemistry at C-25 of 2 was determined by comparative ¹H NMR study using chiral anisotropic reagents [(S)- and (R)-phenylglycine methyl esters]. This is the first to report compound 1 as a natural product.