4356-84-7

The production of glucuronic acid via enzyme catalysis from biomass is slow. Here we studied the oxidation of methoxy-protected glucose (MG) using Pd-on-Au nanoparticle model catalysts to generate methoxy-protected glucuronic acid (MGA), a precursor to glucuronic acid. Pd-on-Au showed volcano-shape activity dependence on calculated Pd surface coverage (sc). The 80 sc% Pd-on-Au catalyst composition showed maximum initial turnover frequency (413 mol-MG mol-surface-atom?1 h?1) that was 5× higher than that of Au/C, while Pd/C was inactive. This Pd-on-Au composition gave the highest MGA yield (46%), supporting a bimetallic approach to glucuronic acid production.

Rhizobia are soil bacteria that form important symbiotic associations with legumes, and rhizobial surface polysaccharides, such as K-antigen polysaccharide (KPS) and lipopolysaccharide (LPS), might be important for symbiosis. Previously, we obtained a mutant of Sinorhizobium fredii HH103, rkpA, that does not produce KPS, a homopolysaccharide of a pseudaminic acid derivative, but whose LPS electrophoretic profile was indistinguishable from that of the WT strain. We also previously demonstrated that the HH103 rkpLMNOPQ operon is responsible for 5-acetamido-3,5,7,9-tetradeoxy-7-(3-hydroxybutyramido)-L-glyc-ero-L-manno-nonulosonic acid [Pse5NAc7(3OHBu)] production and is involved in HH103 KPS and LPS biosynthesis and that an HH103 rkpM mutant cannot produce KPS and displays an altered LPS structure. Here, we analyzed the LPS structure of HH103 rkpA, focusing on the carbohydrate portion, and found that it contains a highly heterogeneous lipid A and a peculiar core oligosaccharide composed of an unusually high number of hexuronic acids containing b-configured Pse5NAc7(3OHBu). This pseudaminic acid derivative, in its a-configuration, was the only structural component of the S. fredii HH103 KPS and, to the best of our knowledge, has never been reported from any other rhizobial LPS. We also show that Pse5NAc7(3OHBu) is the complete or partial epitope for a mAb, NB6-228.22, that can recognize the HH103 LPS, but not those of most of the S. fredii strains tested here. We also show that the LPS from HH103 rkpM is identical to that of HH103 rkpA but devoid of any Pse5NAc7(3OHBu) residues. Notably, this rkpM mutant was severely impaired in symbiosis with its host, Macroptilium atropurpureum.

An effective application development of the polysaccharide ulvan requires a comprehensive knowledge about the influence of the extraction process on composition of the extracts and in ulvan itself. In this context, the two main objectives of the present work are (1) the establishment of an efficient extraction process for ulvan and (2) development of an accurate characterization methodology to evaluate the extract composition and ulvan content. Three ulvan-rich extracts obtained by different schemes of extraction were studied. The methodology for the analysis was improved and a detailed analysis of extracted ulvan was provided. The polysaccharide is rich in ulvanobiuronic acid 3-sulfate type A [→4)-β-d-GlcAp-(1 → 4)-α-l-Rhap 3S-(1→], with minor amounts of ulvanobiuronic acid 3-sulfate type B [→4)-α-l-IdoAp-(1 → 4)-α-l-Rhap 3S-(1→]. The extract with the higher degree of purification is a high molecular weight polysaccharide (790 kDa) composed of rhamnose (22.4%), glucuronic acid (22.5%), xylose (3.7%), iduronic acid (3.1%) and glucose (1.0%). It is highly sulfated (32.2%) and contains 1.3% of proteins and 10.3% of inorganic material. Applying simple extraction scheme it was possible to obtain an extract from green algae with high content of ulvan without affecting the overall chemical structure of the polysaccharide.

Following the characterization of lablabosides A, B, and C, new oleanane-type triterpene bisdesmosides, lablabosides D, E, and F, were isolated from the glycosidic fraction with adjuvant activity obtained from the seeds of Dolichos lablab L. (Leguminosae). Their chemical structures were elucidated on the basis of chemical and physicochemical evidence as follows : 3-O-[α-L-rhamnopyranosyl (1→2)-β-D-galactopyranosyl (1→2)-β-D-glucopyranosiduronic acid]-28-O-[6-O-(3-hydroxy-3-methylglutaroyl)-β-D-glucopyranosyl] 24-epi-hederagenin (lablaboside D), 3-O-[α-L-rhamnopyranosyl (1→2)-β-D-galactopyranosyl (1→2)-β-D-glucopyranosiduronic acid]-28-O-[α-L-rhamnopyranosyl (1→4)-α-L-rhamnopyranosyl (1→2)-β-D-glucopyranosyl] 24-epi-hederagenin (lablaboside E), 3-O-[α-L-rhamnopyranosyl (1→2)-β-D-galactopyranosyl (1→2)-β-D-glucopyranosiduronic acid]-28-O-[α-L-rhamnopyranosyl (1→4)-α-L-rhamnopyranosyl (1→2)-β-D-glucopyranosyl] oleanolic acid (lablaboside F).

Following the characterization of licorice-saponins A3 (2), B2 (3), and C2 (4), the chemical structures of licorice-saponins D3 (5), E2 (6), F3 (7), G2 (8), H2 (9), J2 (10), and K2 (11), seven of the ten oleanane-type triterpene oligoglycosides isolated from the air-dried roots of Glycyrrhiza uralensis FISCHER collected in the northeastern part of China, were investigated. On the basis of chemical and physicochemical evidence, the structures of licorice-saponins D3, E2, F3, G2, H2, J2, and K2 have been determined to be expressed as 3β-[α-L-rhamnopyranosyl(1 → 2)-β-D-glucuronopyranosyl(1 → 2)-β-D-glucuronopyranosyloxy]-22β-acetoxyolean-12-en-30-oic acid (5), 3-O- [β-D-glucuronopyranosyl(1 → 2)-β-D-glucuronopyranosyl]glabrolide (6), 3- O-[α-L-rhamnopyranosyl(1 → 2)-β-D-glucuronopyranosyl(1 → 2)-β-D- glucuronopyranosyl]-11-deoxoglabrolide (7), 24-hydroxyglycyrrhizin (8), 3-O- [β-D-glucuronopyranosyl(1 → 2)-β-D-glucuronopyranosyl]liquiritic acid (9), 24-hydroxy-11-deoxoglycyrrhizin (10), and 3β-[β-D-glucuronopyranosyl(1 → 2)-β-D-glucuronopyranosyloxy]-24-hydroxyoleana-11,13(18)-dien-30-oic acid (11), respectively.

-

-

-

-

-

-

-