Structural characterization of vegetative organs of the endangered Brazilian native species Hesperozygis ringens (Benth.) Epling

The aim of this study was to describe the structural characterization of Hesperozygis ringens (Benth.) Epling vegetative organs. For this purpose, leaves, stems and roots of the endangered Lamiaceae were collected from a population located in Santo Antão, Santa Maria municipality, Rio Grande do Sul, Brazil. Results demonstrated that the H. ringens leaf blade presents glandular and non-glandular trichomes as well as two morphs of diallelocytic stomata, which are usually found above the epidermis level. The petiole is concave on ventral face and convex on its dorsal face, containing glandular and non-glandular trichomes as well as stomata in the epidermis. These types of trichomes were also detected in the stem. In addition, the presence of intercellular spaces within the organ is highlighted. Stomata above epidermis level also occurred in the stem. Phenolic idioblasts were found in the cortical region of plant root and deposit of lipophilic substance was observed in phloem cells. Great amount of apparently two different crystals were detected in all organs. Information obtained in this study provides knowledge about the characterizationof H. ringens, which may be used to distinguish characters of taxa and can help understand the species survival in its occurrence sites.

Analysis of the hydrolysis of inulin using real time 1H NMR spectroscopy

The hydrolysis of various carbohydrates was investigated under acidic conditions in real time by (1)H NMR spectroscopy, with a focus on the polysaccharide inulin. Sucrose was used as a model compound to illustrate the applicability of this technique. The hydrolysis of sucrose was shown to follow pseudo first order kinetics and have an activation energy of 107.0 kJ mol(-1) (SD 1.7 kJ mol(-1)). Inulin, pullulan and glycogen also all followed pseudo first order kinetics, but had an initiation phase at least partially generated by the protonation of the glycosidic bonds. It was also demonstrated that polysaccharide chain length has an effect on the hydrolysis of inulin. For short chain inulin (DPn 18, SD 0.70) the activation energy calculated for the hydrolytic cleavage of glucose was similar to sucrose at 108.5 kJ mol(-1) (SD 0.60). For long chain inulin (DPn 30, SD 1.3) the activation energy for the hydrolytic cleavage of glucose was reduced to 80.5 kJ mol(-1) (SD 2.3 kJ mol(-1)). This anomaly has been attributed to varied conformations for the two different lengths of inulin chain in solution.

Synthesis of 5-(hydroxymethyl)furfural in ionic liquids: paving the way to renewable chemicals

The synthesis of 5-(hydroxymethyl)furfural (HMF) in ionic liquids is a field that has grown rapidly in recent years. Unique dissolving properties for crude biomass in combination with a high selectivity for HMF formation from hexose sugars make ionic liquids attractive reaction media for the production of chemicals from renewable resources. A wide range of new catalytic systems that are unique for the transformation of glucose and fructose to HMF in ionic liquids has been found. However, literature examples of scale-up and process development are still scarce, and future research needs to complement the new chemistry with studies on larger scales in order to find economically and environmentally feasible processes for HMF production in ionic liquids. This Minireview surveys important progress made in catalyst development for the synthesis of HMF in ionic liquids, and proposes future research directions in process technology.

A biologically active fructan from the roots of Arctium lappa L., var. Herkules

From the roots of Arctium lappa L., var. Herkules a low-molecular-weight fructofuranan of the inulin-type has been isolated by water extraction and ethanol precipitation, followed by ion-exchange chromatography and gel filtration of the crude precipitate. The methods employed in structural determination were methylation analysis and 1H and 13C NMR spectral measurements. In tests for antitussive activity in cats the fructan was found to be equally active as some non-narcotic, synthetic preparations used in clinical practice to treat coughing, and in mitogenic and comitogenic tests its biological response was comparable to that of the commercial Zymosan immunomodulator.

Single crystals of inulin

Lamellar crystals of inulin were grown by crystallizing sharp fractions of low molecular weight inulin from dilute aqueous ethanol solutions. The crystals were analyzed using three-dimensional electron diffraction and X-ray powder diagrams. Two crystalline polymorphs were observed, depending on the hydration conditions: a hydrated form which indexed on an orthorhombic unit cell, with space group P2(1)2(1)2(1) and with cell dimensions of a = 1.670 nm, b = 0.980 nm and c (chain axis) = 1.47 nm, together with a pseudo-hexagonal semi-hydrated form with unit cell parameters a = 1.670 nm, b = 0.965 nm and c (chain axis) = 1.44 nm. These parameters, together with the density data, indicate that inulin crystallizes along a pseudo-hexagonal six-fold symmetry with an advance per monomer of 0.24 nm. The difference between the hydrated and the semi-hydrated unit cells does not seem to correspond to any change in the conformation of inulin, but rather to a variation in water content.

Conformational analysis of 1-kestose by molecular mechanics and by n.m.r. spectroscopy

Models of the trisaccharide, 1-kestose [beta-D-fructofuranosyl-(2----1)-beta-D-fructofuranosyl-(2 in equilibrium with 1)-alpha-D -glucopyranoside], were analyzed with the molecular mechanics computer program MM2(87) to ascertain their inter-ring torsion angles, primary alcohol side-group orientations, and ring puckering. The most striking result was that the modeling predicted and n.m.r. spectroscopy corroborated that the central fructofuranose ring takes a different form from that previously observed in the crystal. No other studies of fructofuranoses have observed that crystallographic form, thus suggesting that the 18 hydrogen bonds created upon crystallization of 1-kestose support the ring deformation. Because this trisaccharide is too complex for a complete study of conformation space, only structures having inter-ring conformations that were at energetic valleys in previous studies of the constituent disaccharides were analyzed. The model of the model disaccharides, although they were generally close to the linkage conformations observed in the crystal structure, differing by an average of 19 degrees.

Conformational analysis of inulobiose by molecular mechanics

Conformational energies for inulobiose [beta-D-fructofuranosyl-(2----1)-beta-D-fructofuranoside], a model for inulin, were computed with the molecular mechanics program MMP2(85). The torsion angles of the three linkage bonds were driven in 20 degree increments, and the steric energy of all other parameters was minimized. The linkage torsion angles defined by C-1'-C-2'-O-C-1 (phi) and O-C-1-C-2-O-2 (omega) have minima at +60 degrees and -60 degrees, respectively, regardless of side group orientation; accessible minima exist at other staggered conformations. The torsion angle at the central bond C-2'-O-1-C-1-C-2 (psi) was approximately 180 degrees in all the low-energy conformers. This appears to be generally true for rings linked by three bonds. The fructofuranose rings initially had low-energy 4/3T conformations (angle of pseudorotation, phi 2 = 265 degrees) that were retained except when the linkage conformations created severe inter-residue conflicts. In those cases, almost all puckerings of the furanose rings were found.