Role of clays in the prebiotic synthesis of sugar derivatives from formamide

We describe here the role of montmorillonite KSF in the prebiotic synthesis of amino sugar derivatives starting from a mixture of formamide and formaldehyde as simple chemical precursors. Since amino sugars are key intermediates in the synthesis of complex nucleic acid derivatives, this procedure opens a novel pathway for the formation of nucleosides under plausible primordial conditionsL'articolo é disponibile sul sito dell'editore: http://www.informaworld.co

Obtaining lignin nanoparticles by sonication

Lignin, the main natural aromatic polymer was always aroused researchers interest. Currently around 90% of this biomaterial is burned for energy. It has a very complex and complicated structure which depends on the separation method and plant species, what determine difficulties to use as a raw material widely. This research presents a physical method to modify lignin by ultrasonic irradiation in order to obtain nanoparticles. The nanoparticles synthesized were dimensionally and morphologically characterized. At the same time the preoccupations were to determine the structural and compositional changes that occurred after sonication. To achieve this, two types of commercial lignins (wheat straw and Sarkanda grass) were used and the modifications were analyzed by FTIR-spectroscopy, GPC-chromatography, (31)P-NMR-spectroscopy and HSQC0. The results confirm that the compositional and structural changes of nanoparticles obtained are not significantly modified at the intensity applied but depend on the nature of lignin

Role of clays in the prebiotic synthesis of sugar derivatives from formamide

We describe here the role of montmorillonite KSF in the prebiotic synthesis of amino sugar derivatives starting from a mixture of formamide and formaldehyde as simple chemical precursors. Since amino sugars are key intermediates in the synthesis of complex nucleic acid derivatives, this procedure opens a novel pathway for the formation of nucleosides under plausible primordial conditionsL'articolo é disponibile sul sito dell'editore: http://www.informaworld.co

Tannin Structural Elucidation and Quantitative P-31 NMR Analysis. 1. Model Compounds

Tannins and flavonoids are secondary metabolites of plants that display a wide array of biological activities. This peculiarity is related to the inhibition of extracellular enzymes that occurs through the complexation of peptides by tannins. Not only the nature of these interactions, but more fundamentally also the structure of these heterogeneous polyphenolic molecules are not completely clear. This first paper describes the development of a new analytical method for the structural characterization of tannins on the basis of tannin model compounds employing an in situ labeling of all labile H groups (aliphatic OH, phenolic OH, and carboxylic acids) with a phosphorus reagent. The P-31 NMR analysis of P-31 labeled samples allowed the unprecedented quantitative and qualitative structural characterization of hydrolyzable tannins, proanthocyanidins, and catechin tannin model compounds, forming the foundations for the quantitative structural elucidation of a variety of actual tannin samples described in part 2 of this series

An efficient and stereoselective dearylation of asarinin and sesamin tetrahydrofurofuran lignans to acuminatolide by methyltrioxorhenium/H2O2 and UHP systems

The synthesis of stereoisomers of acuminatolide is rare and requires complex and time-consuming multistep procedures. Asarinin (1) and sesamin (2), two diasteromeric tetrahydrofurofuran lignans, are efficiently mono-dearylated by methyltrioxorhenium (MTO, I) and hydrogen peroxide (H2O2) or urea hydrogen peroxide adduct (UHP) as primary oxidant to give (-)-(7R,8'R,8R)-acuminatolide (3A) and (+)-(7S,8R,8'R)-acuminatolide (3B), respectively, in high yield and diastereoselectivity (de > 98%). The oxidation of 1 was also performed with novel heterogeneous catalysts based on the heterogenation of MTO on poly(4-vinylpyridine) and polystyrene resins. In these latter cases 3A was obtained with a different yield and selectivity depending on the physical-chemical properties of the support. Cytotoxic effects of 3A and 3B in mammalian cell lines in vitro are also reported

Tailoring the molecular and thermo-mechanical properties of kraft lignin by ultrafiltration

This study has shown that ultrafiltration allows the selective extraction from industrial black liquors of lignin fraction with specific thermo-mechanical properties, which can be matched to the intended end uses. Ultrafiltration resulted in the efficient fractionation of kraft lignin according to its molecular weight, with an accumulation of sulfur-containing compounds in the low-molecular weight fractions. The obtained lignin samples had a varying quantities of functional groups, which correlated with their molecular weight with decreased molecular size, the lignin fractions had a higher amount of phenolic hydroxyl groups and fewer aliphatic hydroxyl groups. Depending on the molecular weight, glass-transition temperatures (Tg) between 70 and 170C were obtained for lignin samples isolated from the same batch of black liquor, a tendency confirmed by two independent methods, DSC, and dynamic rheology (DMA). The Fox-Flory equation adequately described the relationship between the number average molecular masses (Mn) and Tg's-irrespective of the method applied. DMA showed that low-molecular-weight lignin exhibits a good flow behavior as well as high-temperature crosslinking capability. Unfractionated and high molecular weight lignin (Mw>5 kDa), on the other hand, do not soften sufficiently and may require additional modifications for use in thermal processings where melt-flow is required as the first step. Copyright © 2014 Wiley Periodicals, Inc

Driven Assembly of Lignin into Microcapsules for Storage and Delivery of Hydrophobic Molecules

Oil-filled microcapsules of kraft lignin were synthe- sized by first creating an oil in water emulsion followed by a high- intensity, ultrasound-assisted cross-linking of lignin at the water/oil interface. The rationale behind our approach is based on promoting documented lignin hydrophobic interactions within the oil phase, followed by locking the resulting spherical microsystems by covalent cross-linking using a high intensity ultrasound treatment. As further evidence in support of our rationale, confocal and optical microscopies demonstrated the uniformly spherical morphology of the created lignin microparticles. The detailed elucidation of the cross-linking processes was carried out using gel permeation chromatography (GPC) and quantitative 31P NMR analyses. The ability of lignin microcapsules to incorporate and release Coumarin-6 was evaluated in detail. In vitro studies and confocal laser scanning microscopy analysis were carried out to assess the internalization of capsules into Chinese hamster ovary (CHO) cells. This part of our work demonstrated that the lignin microcapsules are not cytotoxic and readily incorporated in the CHO cells