Rhamnose Derivatives Research Articles

Functional analysis of PpRHM1 and PpRHM2 involved in UDP-l-rhamnose biosynthesis in Prunus persica

UDP-l-rhamnose (UDP-Rha) is an important sugar donor for glycosylation of various cell molecules in plant. Rhamnosides are widely present in different plant tissues and play important biological roles under different developmental or environmental conditions. However, enzymes involved in UDP-Rha biosynthesis and their encoding genes have been identified in few plants, which limits the functional analysis of plant rhamnosides. Here, two UDP-Rha biosynthesis genes, named PpRHM1 (2028 bp) and PpRHM2 (2016 bp), were isolated and characterized from Prunus persica, which is rich sources of flavonol rhamnosides. Both recombinant RHM proteins can catalyze the transformation from UDP-d-glucose (UDP-Glc) to UDP-Rha, which was confirmed by LC-MS and formation of flavonol rhamnosides. Biochemical analysis showed that both recombinant RHM proteins preferred alkaline conditions in pH range of 8.0–9.0 and had optimal reaction temperature between 25 and 30 °C. PpRHM1 showed the better UDP-Glc substrate affinity with Km of 360.01 μM. Gene expression analysis showed different transcript levels of both RHMs in all plant tissues tested, indicating the involvement of rhamnosides in various tissues in plant. Such results provide better understanding of UDP-Rha biosynthesis in fruit tree and may be helpful for further investigation of various rhamnose derivatives and their biological functions.

Water Dispersible Carbohydrate-Coated Ferrite Nanoparticles. Effect of Cobalt Doping in Magneto-Thermal Properties

Water dispersible cobalt ferrite nanoparticles, CoxFe3-xO₄, of different size (4-10 nm) and various composition (0 ≤ x ≤ 1), functionalized with a rhamnose derivative were obtained and characterized by combining TEM, XRD and elemental analyses techniques. Magnetic properties of these systems were studied by SQUID magnetometry. A particular emphasis was given to the investigation of magnetocrystalline anisotropy and size effect on the heating abilities of the nanoparticles under the application of an alternating magnetic field.

A semisynthesis of 3'-O-ethyl-5,6-dihydrospinosyn J based on the spinosyn A aglycone.

Spinetoram, a mixture of 3'-O-ethyl-5,6-dihydrospinosyn J (XDE-175-J, major component) and 3'-O-ethylspinosyn L (XDE-175-L, minor component), is a novel kind of green and efficient insecticide with a broad range of action against various insects. Nowadays, spinetoram is widely used in agriculture and food storage. This work reports a 7-step semisynthesis of 3'-O-ethyl-5,6-dihydrospinosyn J from spinosyn A aglycone. The C9–OH and C17–OH of the aglycone are successively connected to 3-O-ethyl-2,4-di-O-methylrhamnose and D-forosamine after selective protection and deprotection steps. Then, with 10% Pd/C as catalyst, the 5,6-double bond of the macrolide was selectively reduced to afford 3'-O-ethyl-5,6-dihydrospinosyn J. In addition, the 3-O-ethyl-2,4-di-O-methylrhamnose is synthesized from rhamnose which is available commercially, while the D-forosamine and aglycone are obtained via the hydrolysis of spinosyn A. High yields were obtained in each step, and all intermediates in the synthesis were characterized by 1H NMR, 13C NMR and MS techniques. This study can be helpful for developing an efficient chemical synthesis of spinetoram, and it also offers opportunities to synthesize spinosyn analogues and rhamnose derivatives.

Rhamnose-coated superparamagnetic iron-oxide nanoparticles: an evaluation of their in vitro cytotoxicity, genotoxicity and carcinogenicity.

Tumor recurrence after the incomplete removal of a tumor mass inside brain tissue is the main reason that scientists are working to identify new strategies in brain oncologic therapy. In particular, in the treatment of the most malignant astrocytic tumor glioblastoma, the use of magnetic nanoparticles seems to be one of the most promising keys in overcoming this problem, namely by means of magnetic fluid hyperthermia (MFH) treatment. However, the major unknown issue related to the use of nanoparticles is their toxicological behavior when they are in contact with biological tissues. In the present study, we investigated the interaction of glioblastoma and other tumor cell lines with superparamagnetic iron-oxide nanoparticles covalently coated with a rhamnose derivative, using proper cytotoxic assays. In the present study, we focused our attention on different strategies of toxicity evaluation comparing different cytotoxicological approaches in order to identify the biological damages induced by the nanoparticles. The data show an intensive internalization process of rhamnose-coated iron oxide nanoparticles by the cells, suggesting that rhamnose moiety is a promising biocompatible coating in favoring cells' uptake. With regards to cytotoxicity, a 35% cell death at a maximum concentration, mainly as a result of mitochondrial damages, was found. This cytotoxic behavior, along with the high uptake ability, could facilitate the use of these rhamnose-coated iron-oxide nanoparticles for future MFH therapeutic treatments.

The first total synthesis and structural determination of antibiotics K1115 B1s (alnumycins)

K1115 B1, isolated from the broth of Streptomyces species, was found to be a mixture of stereoisomers. Authors synthesized all stereoisomers of K1115 B1 by convergent synthesis coupling a rhamnose derivative, an isobenzofuranone, and a chiral tetraol. Comparison of 1H NMR spectra and optical rotations made it clear that the absolute structures of K1115 B1α (the major isomer) and K1115 B1β (the minor isomer) were (1R, 17S)- and (1R, 17R)-configurations, respectively. The optical rotations of the stereoisomers revealed that alnumycin, reported as the identical structure with K1115 B1, might be another mixture of stereoisomers.

Morphology and physico-chemical properties of Bacillus spores surrounded or not with an exosporium : Consequences on their ability to adhere to stainless steel

This study was designed to elucidate the influence of spore properties such as the presence of an exosporium, on their ability to adhere to materials. This analysis was performed on 17 strains belonging to the B. cereus group and to less related Bacillus species. We first demonstrated that spores of the B. cereus group, surrounded by an exosporium, differed in their morphological features such as exosporium size, number of appendages or hair-like nap length. We also found that the saccharidic composition of exosporium differed among strains, e.g. concerning a newly identified rhamnose derivative: the 2,4-O-dimethyl-rhamnose. Conversely, spores of distant Bacillus species shared morphological and physico-chemical properties with B. cereus spores. Some external features were also observed on these spores, such as a thin loose-fitting layer, whose nature is still to be determined, or a thick saccharidic layer (mainly composed of rhamnose and quinovose). The ability of spores to adhere to stainless steel varied among strains, those belonging to the B. cereus group generally being the most adherent. However, the presence of an exosporium is not sufficient to explain the ability of spores to adhere to inanimate surfaces. Indeed, when the 17 strains were compared, hydrophobicity and the number of appendages were the only significant adhesion parameters. Furthermore, the differences in spore adhesion observed within the B. cereus group were related to differences in the number of appendages, the exosporium length and to a lesser extent, the zeta potential.

Synthesis of rhamnogalacturonan I fragments by a modular design principle

The improved syntheses of methyl 2- O-acetyl-3- O-benzyl-α- l-rhamnopyranoside ( 12) and 1,2-di- O-acetyl-3- O-benzyl-α- l-rhamnopyranose ( 15), which were used as glycosyl acceptor and donor, respectively, are described. Glycosylation of the O-4 position of both rhamnose derivatives with 2,3,4,6-tetra- O-benzoyl-α- d-galactopyranosyl bromide ( 26) provided disaccharides 27 and 29. After partial deprotection of 27 and coupling of the resulting 28 with disaccharide 19, tetrasaccharide 31 was obtained. Furthermore, transforming of 29 into the corresponding bromide 30 and coupling with galacturonates 16 and 32 provided trisaccharides 33 and 34, respectively, which could be regarded as building blocks of ramified rhamnogalacturonan fragments. The preparation of tetra- ( 21) and hexasaccharide ( 25) of rhamnogalacturonan I is reported to demonstrate the feasibility of the synthesis of larger pectin fragments using the modular design principle with this type of building blocks.

Chlorosome lipids from Chlorobium tepidum: characterization and quantification of polar lipids and wax esters

We have extracted polar lipids and waxes from isolated chlorosomes from the green sulfur bacterium Chlorobium tepidum and determined the fatty acid composition of each lipid class. Polar lipids amounted to 4.8 mol per 100 mol bacteriochlorophyll in the chlorosomes, while non-polar lipids (waxes) were present at a ratio of 5.9 mol per 100 mol bacteriochlorophyll. Glycolipids constitute 60 % of the polar lipids while phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, and an aminoglycosphingolipid make up respectively 15, 3, 8 and 12 %. A novel glycolipid was identified as a rhamnose derivative of monogalactosyldiacylglycerol, while the other major glycolipid was monogalactosyldiacylglycerol. Tetradecanoic acid was the major fatty acid in the aminoglycosphingolipid, while the other polar lipids contained predominantly hexandecanoic acid. The chlorosome waxes are esters of unbranched fatty acids and fatty alcohols with 14 or 16 carbon atoms, joined to form molecules with between 28 and 32 carbon atoms. The stoichiometry between lipids and bacteriochlorophyll suggests that much of the chlorosome surface is covered by protein.

Synthesis of the trisaccharide portion of soyasaponin βg: evaluation of a new glucuronic acid acceptor

The synthesis of the trisaccharide portion of soyasaponin βg was successfully achieved using a new glucuronic acid acceptor: methyl 1- O-allyl-3,4-di- O-methoxymethyl-β- d-glucuronate ( 9). This compound and methyl 1- O-allyl-3,4-di- O- tert-butyldimethylsilyl-β- d-glucuronate ( 8) were both prepared from glucuronolactone via a glycal intermediate. The former compound 9 was successfully coupled to ethyl 2- O-benzoyl-3,4,6-tri- O-benzyl-1-thio-β- d-galactopyranoside ( 13) in excellent yield. Synthesis of the protected trisaccharide was then completed by the addition of a suitably protected rhamnose derivative to the disaccharide portion. The reactivity of the glucuronic acid derivative 9 was also explored with trichloroacetimidate and fluoride donors.

Synthesis of the endothelin converting enzyme inhibitor phosphoramidon

Phosphoramidon, an endothelin converting enzyme inhibitor, is synthesized by coupling of a rhamnose derivative with a dichlorophosphate and a suitably protected dipeptide.

Infrared study of intramolecular hydrogen bonds in α-?-rhamnose derivatives in solution

Infrared study of intramolecular hydrogen bonds in α-?-rhamnose derivatives in solution

Synthesis of oligosaccharides corresponding to the antigenic determinants of the β-haemolytic Streptococci Group A. Part 1. Overall strategy and synthesis of a linear trisaccharide

The overall strategy for the synthesis of higher-order oligosaccharides corresponding to the repeating unit of the cell-wall polysaccharide of the β-haemolytic Streptococci Group A is described. The trisaccharide, β-D-GlcpNAc-(1→3)-α-L-Rhap-(1→3)-α-L-Rhap has been synthesized by a series of Königs-Knorr reactions. The selectively protected rhamnose derivative, allyl 2-O-benzoyl-4-O-benzyl-α-L-rhamnopyranoside, reacted with 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-D-glucopyranosyl bromide to give the blocked disaccharide. Deallylation, followed by treatment with N,N-dimethyl(chloromethylene)ammonium chloride then gave the corresponding disaccharide chloride. In conjunction with the same rhamnose monosaccharide unit or 8-methoxycarbonyloctyl 2,4-di-O-benzoyl-α-L-rhamnopyranoside, the synthesis of the blocked trisaccharide, as its allyl glycoside or its 8-methoxycarbonyloctyl glycoside, respectively, was accomplished. Transesterification, followed by hydrazinolysis, selective N-acetylation, and hydrogenolysis afforded the pure trisaccharide, as its propyl glycoside or 8-methoxycarbonyloctyl glycoside, for use as a hapten in binding studies and n.m.r. studies or for use in the preparation of glycoconjugates, respectively. Similar treatment of the blocked disaccharide afforded the hapten, β-D-GlcpNAc-(1→3)-α-LRhap, as its propyl glycoside.

Strategies for the synthesis of branched oligosaccharides of the Shigella flexneri 5a, 5b, and variant X serogroups employing a multifunctional rhamnose precursor

Allylation of methyl 2-O-benzoyl-4-O-benzyl-α-L-rhamnopyranoside (4) using allyl trichloroacetimidate under mildly acidic conditions provides the multifunctional rhamnose derivative (7). Glycosylation of the vicinal O-2 and O-3 positions of this derivative in either sequence permitted the synthesis, in good yield, of a branched trisaccharide (24) corresponding to a crucial portion of the Shigella flexneri variant X O-antigen. The flexibility of the derivative (7) was further demonstrated by the synthesis of a tetrasaccharide (36) containing the branch point of the S. flexneri serogroup 5a antigen. Attempts to synthesize the pentasaccharide (39) corresponding to the branched S. flexneri serogroup 5b antigen were hampered by the low yields and poor stereospecificity of the α-glucosylation reactions.

The Synthesis of some 1-glycosyl-6-nitroindoles

Condensation of 6-nitroindoline with 5- O-trityl- L-arabinose, - D-fucose, - D-arabinose, or - L-rhamnose gave the corresponding 1-glycosyl-6-nitroindolines, from which, after acetylation, dehydrogenation, and removal of protecting groups, 1-α-and -β- L-arabinofuranosyl, 1-β- D-fucopyranosyl, 1-α- D-arabinopyranosyl, and 1-α-and -β- L-rhamnopyranosyl derivatives of 6-nitroindole were obtained. The configuration of the arabinose and fucose derivatives was established by p.m.r. spectroscopy. Comparison of the p.m.r. and c.d. spectra of the products obtained from the glycosyl-nitroindoles by application in sequence of periodate oxidation, borohydride reduction, and acetylation allowed assignment of the configuration of the rhamnose derivatives.

Proton magnetic resonance spectra of ethyl 3-(glycosylamino)crotonates

The p.m.r. spectra of ethyl 3-(glycosylamino)crotonates derived from d-glucose, d-galactose, d-mannose, and l-rhamnose, and those of their corresponding O-acetyl derivatives, have been examined. The results confirm that the amino and ethoxy-carbonyl groups of the enamine portion of these substances are in cis disposition and intramolecularly bonded. No other isomeric or tautomeric forms could be detected under the conditions used. Pyranose ring sizes and anomeric configurations (gb- l for the rhamnose derivative, and β- d for the remaining compounds) are assigned to the O-acetyl derivatives on the basis of the chemical shifts and coupling constants observed. The same pyranose structures and anomeric configurations are proposed for the parent compounds after considering the chemical shifts and coupling constants of the anomeric protons.

Isolation of Rhamnose Derivatives from Ulva lactuca

WORKING on algae other than the Chlorophyceae, various investigators have established the existence of algal polysaccharides containing mannuronic, galactose or fucose residues, the two latter being in the form of sulphuric acid esters. An investigation of Ulva lactuca, a member of the Chlorophyceae, undertaken with the hope of ultimate correlation with pigmentation, has unexpectedly revealed the presence of a rhamnose polysaccharide, hitherto unknown among algal products.