The chemistry and biological activity of the Hyacinthaceae

Covering: 1914 to 2012The Hyacinthaceae (sensu APGII), with approximately 900 species in about 70 genera, can be divided into three main subfamilies, the Hyacinthoideae, the Urgineoideae and the Ornithogaloideae, with a small fourth subfamily the Oziroëoideae, restricted to South America. The plants included in this family have long been used in traditional medicine for a wide range of medicinal applications. This, together with some significant toxicity to livestock has led to the chemical composition of many of the species being investigated. The compounds found are, for the most part, subfamily-restricted, with homoisoflavanones and spirocyclic nortriterpenoids characterising the Hyacinthoideae, bufadienolides characterising the Urgineoideae, and cardenolides and steroidal glycosides characterising the Ornithogaloideae. The phytochemical profiles of 38 genera of the Hyacinthaceae will be discussed as well as any biological activity associated with both crude extracts and compounds isolated. The Hyacinthaceae of southern Africa were last reviewed in 2000 (T. S. Pohl, N. R. Crouch and D. A. Mulholland, Curr. Org. Chem., 2000, 4, 1287-1324; ); the current contribution considers the family at a global level

The biofilm matrix of Pseudomonas sp. OX1 grown on phenol is mainly constituted by alginate oligosaccharides

The structure of the major constituent of the biofilm matrix produced by Pseudomonas sp. OX1, when grown on phenol as the sole carbon source is described. This investigation, carried out by chemical analysis, NMR spectroscopy and MALDI-TOF MS spectrometry, showed the presence of an oligosaccharide blend with the typical alginate structure, namely (1-->4) substituted beta-D-mannuronic (ManA) and alpha-L-guluronic acid (GulA). GulA residues were non-acetylated whereas ManA was always O-acetylated at C-2 or C-3

Identification and structural determination of the capsular polysaccharides from two Acinetobacter baumannii clinical isolates, MG1 and SMAL

The structures of the capsular polysaccharides (CPSs) of the two clinical isolates Acinetobacter baumannii SMAL and MG1 were elucidated. Hot phenol/water extractions of the dry biomasses, followed by enzymatic digestions and repeated ultracentrifugations led to the isolation of polysaccharides that were negative in Western blot analysis utilizing an anti-lipid A antibody, thus proving that they were not the LPS O-antigens but CPSs. Their structures were established on the basis of NMR spectroscopy and GC-MS analyses. The A. baumannii MG1 CPS consisted of a linear aminopolysaccharide with acyl substitution heterogeneity at the N-4 amino group of QuipN4N: 4)-alpha-D-GlcpNAc-(1 -> 4)-alpha-L-GalpNAcA-(1 -> 3)-beta-D-QuipNAc4NR-(1 -> R = -3-hydroxybutyrryl or acetyl. The repeating unit of the CPS produced by strain SMAL is a pentasaccharide, already reported for the O-antigen moiety from A. baumannii strain ATCC 17961: beta-D-GlcpNAc3NAcA-(1 down arrow 4) 6)-beta-D-Glcp-(1 -> 3)-beta-D-GalpNAc-(1 -> 3)-alpha-D-Galp-(1 -> 6)up arrow beta-D-GlcpNAc-(

Structural Investigation of the Oligosaccharide Portion Isolated from the Lipooligosaccharide of the Permafrost Psychrophile Psychrobacter arcticus 273-4

Psychrophilic microorganisms have successfully colonized all permanently cold environments from the deep sea to mountain and polar regions. The ability of an organism to survive and grow in cryoenviroments depends on a number of adaptive strategies aimed at maintaining vital cellular functions at subzero temperatures, which include the structural modifications of the membrane. To understand the role of the membrane in the adaptation, it is necessary to characterize the cell-wall components, such as the lipopolysaccharides, that represent the major constituent of the outer membrane. The aim of this study was to investigate the structure of the carbohydrate backbone of the lipooligosaccharide (LOS) isolated from the cold-adapted Psychrobacter arcticus 273-4. The strain, isolated from a 20,000-to-30,000-year-old continuously frozen permafrost in Siberia, was cultivated at 4 °C. The LOS was isolated from dry cells and analyzed by means of chemical methods. In particular, it was degraded either by mild acid hydrolysis or by hydrazinolysis and investigated in detail by (1)H and (13)C NMR spectroscopy and by ESI FT-ICR mass spectrometry. The oligosaccharide was characterized by the substitution of the heptose residue, usually linked to Kdo in the inner core, with a glucose, and for the unusual presence of N-acetylmuramic acid

Structural characterisation of endotoxins from marine and halophilic bacteria

Gram-negative bacteria cell envelope is a complex structure that is constantly exposed to its environment. It is composed of an Inner-membrane (IM), a thin peptidoglycan layer and an Outer-membrane (OM). The main component of the OM are Lipopolysaccharides (LPS), also termed as endotoxins. Those molecules are composed of three main parts: a polysaccharide named the O-antigen, a core oligosaccharide and a Lipid A. Endotoxins lacking the polysaccharide are termed Lipooligosaccharides (LOS). LPS are known to interact with mammal’s innate immunity through the Toll-like receptor 4 (TLR4) and Myeloid Differentiation factor 2 (MD-2) receptorial complex. Depending on their structure, and in particular on their Lipid A, LPS can either have an agonist or an antagonist activity. Discovering new LPS structure is hence necessary in order to develop new therapies, since agonist LPS can be used as vaccines adjuvant and antagonist as drugs against sepsis and septic shock. In this context, LPS structures from various bacterial sources are currently under study. This project present the characterization of LPS and LOS extracted from marine and halophilic bacteria. As those organisms live in a particular environment, they developed specific strategies to adapt themselves and were hence investigated, as their LPS structure can be shaped by the adaptation to their environment. In particular, the study of LPS from the following strains is here reported. Pseudoalteromonas sp1A1 is a sponge-pathogen bacterium isolated from Suberites domuncula. The full structure of its LPS was resolved using NMR spectroscopy and Matrix assisted laser desorption (MALDI) Mass spectrometry (MS). Its O-antigen is a branched polysaccharide that have two remarkable features: (i) it possesses a pyruvate linked at 4,6-position of a Glucosamine and (ii) it possesses a 9-carbon ulosonic acid that is the 3-deoxy-D-glycero-D-galacto-nonulosonic acid (KDN). The Lipid A from Pseudoalteromonas sp1A1 was studied by MALDI MS. It is constituted of a mixture of tri- to penta-acylated species, among the penta-acylated Lipid A species, at m/z 1474.6 and 1446.6 were bis-phosphorylated species composed respectively of four C12:0 (3-OH) and one C12:0 and two C12:0 (3-OH), one C10:0 (3-OH), one C11:0 (3-OH) and one C13:0. The structure of the core oligosaccharide from Pseudoalteromonas sp1A1 LPS was also resolved and turned out to be composed of a pentasaccharide containing one Kdo, one heptose, two galactoses and one glucose. Pseudoalteromonas sp1A1 biological activity was assessed using ELISA and Quanti-blue assays. It was found that its LPS does not possess any significant immunostimulant activity on human and murine cells. The Outer-Membrane properties of Pseudoalteromonas sp1A1 were also studied through Molecular Dynamic (MD) simulation, that showed how the asymmetric repartition of Pseudoalteromonas sp1A1 Lipid A influenced the properties of the phospholipid bilayer, increasing its flexibility. Finally, MD simulation was also performed with Pseudoalteromonas sp1A1 LOS in water and in 0.5 M of NaCl, that is closed to the natural marine environment of the bacterium. Results showed that the presence of salts influenced the conformational behavior of the Kdo-Lipid A region. The second bacterial strain studied was Spiribacter salinus M19-40T, a halophile isolated from an intermediate salinity pound of a marine saltern in Spain, the structure of the Lipid A was resolved using MALDI MS and MS2 experiment. It is a mono-phosphorylated and penta-acylated species bearing two C10:0 (3-OH), one C12:0, one C14:0 (3-OH) and one C14:0 (3-oxo). This structure possesses two interesting structural features: (i) the 2+3 symmetry that is unusual - as most penta-acylated Lipid A have a 3+3 symmetry and (ii) the occurrence of the C14:0 (3-oxo). Halopeptonella vilamensis is a halophilic bacterium that have been isolated from a saline lagoon in Argentina whose Lipid A was characterized using MALDI MS and MS2 experiments. Results showed that H. vilamensis has a highly heterogeneous mixture of Lipid A species, mono-phosphorylated and hexa-acylated, that differ for the length and saturation of their acyl chains. H. vilamensis main Lipid A species possesses two C10:0 (3-OH), two C12:0 (3-OH), one C12:0 and one C12:1. Another major species possesses only saturated C12:0. Immunological assays were performed on HEK293 hTLR4/CD14/MD2 murine cell line and on Monocytes-derived Macrophages (MoMs) and Bone marrow-derived macrophages (BMDMs) human cell lines with H. vilamensis LOS and demonstrated its slight immunopotency. Finally, the characterization of cell envelope components of Halomonas smyrnensis was also attempted. H. smyrnensis is an Exopolysaccharide (EPS) producing halophile isolated from a Turkish salt lake. It is known to be a high levan producer and two novel EPS were isolated. The first one is formed by α-(1→4)-Glc polymer and the second one by α-(1→3)-GlcNAc units

Molecular Structure of Endotoxins from Gram-negative Marine Bacteria: An Update

Marine bacteria are microrganisms that have adapted, through millions of years, to survival in environments often characterized by one or more extreme physical or chemical parameters, namely pressure, temperature and salinity. The main interest in the research on marine bacteria is due to their ability to produce several biologically active molecules, such as antibiotics, toxins and antitoxins, antitumor and antimicrobial agents. Nonetheless, lipopolysaccharides (LPSs), or their portions, from Gram-negative marine bacteria, have often shown low virulence, and represent potential candidates in the development of drugs to prevent septic shock. Besides, the molecular architecture of such molecules is related to the possibility of thriving in marine habitats, shielding the cell from the disrupting action of natural stress factors. Over the last few years, the depiction of a variety of structures of lipids A, core oligosaccharides and O-specific polysaccharides from LPSs of marine microrganisms has been given. In particular, here we will examine the most recently encountered structures for bacteria belonging to the genera Shewanella, Pseudoalteromonas and Alteromonas, of the γ-Proteobacteria phylum, and to the genera Flavobacterium, Cellulophaga, Arenibacter and Chryseobacterium, of the Cytophaga-Flavobacterium-Bacteroides phylum. Particular attention will be paid to the chemical features expressed by these structures (characteristic monosaccharides, non-glycidic appendages, phosphate groups), to the typifying traits of LPSs from marine bacteria and to the possible correlation existing between such features and the adaptation, over years, of bacteria to marine environments

Detailed Structural Characterization of the Lipooligosaccharide from the Extracellular Membrane Vesicles of Shewanella vesiculosa HM13

Bacterial extracellular membrane vesicles (EMVs) are membrane-bound particles released during cell growth by a variety of microorganisms, among which are cold-adapted bacteria. Shewanella vesiculosa HM13, a cold-adapted Gram-negative bacterium isolated from the intestine of a horse mackerel, is able to produce a large amount of EMVs. S. vesiculosa HM13 has been found to include a cargo protein, P49, in the EMVs, but the entire mechanism in which P49 is preferentially included in the vesicles has still not been completely deciphered. Given these premises, and since the structural study of the components of the EMVs is crucial for deciphering the P49 transport mechanism, in this study the complete characterization of the lipooligosaccharide (LOS) isolated from the cells and from the EMVs of S. vesiculosa HM13 grown at 18 °C is reported. Both lipid A and core oligosaccharide have been characterized by chemical and spectroscopic methods

Structural characterization of an all-aminosugar-containing capsular polysaccharide from Colwellia psychrerythraea 34H

Colwellia psychrerythraea strain 34H, a Gram-negative bacterium isolated from Arctic marine sediments, is considered a model to study the adaptation to cold environments. Recently, we demonstrated that C. psychrerythraea 34H produces two different extracellular polysaccharides, a capsular polysaccharide and a medium released polysaccharide, which confer cryoprotection to the bacterium. In this study, we report the structure of an additional capsular polysaccharide produced by Colwellia grown at a different temperature. The structure was determined using chemical methods, and one- and two-dimensional NMR spectroscopy. The results showed a trisaccharide repeating unit made up of only amino-sugar residues: N-acetyl-galactosamine, 2,4-diacetamido-2,4,6-trideoxy-glucose (bacillosamine), and 2-acetamido-2-deoxyglucuronic acid with the following structure: →4)-β-d-GlcpNAcA-(1 →3)-β-d-QuipNAc4NAc-(1 →3)-β-d-GalpNAc-(1 →. The 3D model, generated in accordance with 1H,1H-NOE NMR correlations and consisting of ten repeating units, shows a helical structure. In contrast with the other extracellular polysaccharides produced from Colwellia at 4 °C, this molecule displays only a low ice recrystallization inhibition activity