Eric Grand

Selective TEMPO‐Catalyzed Chemicals vs. Electrochemical Oxidation of Carbohydrate Derivatives

TEMPO‐catalyzed electrochemical oxidation of carbohydrate derivatives was performed and compared with chemical oxidation, which requires the use of co‐oxidants. Allyl‐protected derivatives could be readily oxidized by both methods. Electrochemical selective oxidation of primary positions has been adapted to unprotected mono‐ and oligosaccharides.

Synthesis of sugar-based chelating surfactants for metal removal from wastewater

Four chelating surfactants were synthesized in a few steps from octyl D-glucosides. Their main interfacial properties were determined, and their flotation properties were evaluated on a laboratory scale using Fe(III) as a model contaminant metal. The performance on metal extraction was mainly dependent on the complexing functional group, but the surfactant efficiency was also important.

Synthesis of peracetylated chacotriose

Steroidal glycoalkaloids of many Solanum species have recognized biological activities, especially those containing the glycosyl moiety alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->4)]-D-glucopyranose (chacotriose) whose peracetate is here synthesized and characterized by complete 1H and 13C NMR assignment.

Physico-chemical properties and cytotoxic effects of sugar-based surfactants: Impact of structural variations

Surfactants derived from the biorefinery process can present interesting surface-active properties, low cytotoxicity, high biocompatibility and biodegradability. They are therefore considered as potential sustainable substitutes to currently used petroleum-based surfactants. To better understand and anticipate their performances, structure-property relationships need to be carefully investigated. For this reason, we applied a multidisciplinary approach to systematically explore the effect of subtle structural variations on both physico-chemical properties and biological effects. Four sugar-based surfactants, each with an eight carbon alkyl chain bound to a glucose or maltose head group by an amide linkage, were synthesized and evaluated together along with two commercially available standard surfactants. Physico-chemical properties including solubility, Krafft point, surface-tension lowering and critical micellar concentration (CMC) in water and biological medium were explored. Cytotoxicity evaluation by measuring proliferation index and metabolic activity against dermal fibroblasts showed that all surfactants studied may induce cell death at low concentrations (below their CMC). Results revealed significant differences in both physico-chemical properties and cytotoxic effects depending on molecule structural features, such as the position of the linkage on the sugar head-group, or the orientation of the amide linkage. Furthermore, the cytotoxic response increased with the reduction of surfactant CMC. This study underscores the relevance of a methodical and multidisciplinary approach that enables the consideration of surfactant solution properties when applied to biological materials. Overall, our results will contribute to a better understanding of the concomitant impact of surfactant structure at physico-chemical and biological levels.

Microwave-Assisted Extraction of Herbacetin Diglucoside from Flax (Linum usitatissimum L.) Seed Cakes and Its Quantification using an RP-HPLC-UV System

Flax (Linum usitatissimum L.) seeds are widely used for oil extraction and the cold-pressed flaxseed (or linseed) cakes obtained during this process constitute a valuable by-product. The flavonol herbacetin diglucoside (HDG) has been previously reported as a constituent of the flaxseed lignan macromolecule linked through ester bonds to the linker molecule hydroxymethylglutaric acid. In this context, the development and validation of a new approach using microwave-assisted extraction (MAE) of HDG from flaxseed cakes followed by quantification with a reverse-phase HPLC system with UV detection was purposed. The experimental parameters affecting the HDG extraction yield, such as microwave power, extraction time and sodium hydroxide concentration, from the lignan macromolecule were optimized. A maximum HDG concentration of 5.76 mg/g DW in flaxseed cakes was measured following an irradiation time of 6 min, for a microwave power of 150 W using a direct extraction in 0.1 M NaOH in 70% (v/v) aqueous methanol. The optimized method was proven to be rapid and reliable in terms of precision, repeatability, stability and accuracy for the extraction of HDG. Comparison with a conventional extraction method demonstrated that MAE is more effective and less time-consuming.

UV-MALDI-TOF Mass Spectrometry Analysis of Heparin Oligosaccharides Obtained by Nitrous Acid Controlled Degradation and High Performance Anion Exchange Chromatography

Nitrous acid degradation of heparin followed by high-performance anion-exchange chromatography (HPAEC) separation and ultraviolet matrix assisted laser desorption/ionization time-of-flight (UV-MALDI-TOF) analysis led to the structural determination of six sulfated oligosaccharides. Three different matrices (α-cyano-4-hydroxycinnamic acid (CHCA), nor-harmane, and dihydroxybenzoic acid (DHB)) have been used, and the complementary results obtained allowed in most cases to assign the position of sulfate groups. Based on the different cleavages produced on the purified oligosaccharides in source during the MS analysis by the use of the different matrices, this approach provides a new tool for structural analysis.

Microwave-assisted synthesis of long-chain alkyl glucopyranosides

Long-chain (C(6) to C(16)) alkyl glucopyranosides have been synthesized using microwave irradiation. Yields and anomeric ratios can be controlled under precise and short irradiation times (few min). Comparison with classical heating showed a better efficiency of microwaves.

Synthesis of a trisulfated heparan sulfate disaccharide analog and its use as a template for preliminary molecular imprinting studies.

A heparan sulfate disaccharide analog was synthesized by a multistep route. This synthesis was designed in such a way that one intermediate could be selectively deprotected to provide versatility during both synthesis and homologation of heparan sulfate related polysaccharides. Non-covalent imprinted polymers were prepared by using the synthesized disaccharide as a template and a primary amine functionalized acrylate as the key functional monomer suitable for specific sulfated sugar recognition. The binding of related sugars to the imprinted and non-imprinted polymers and the binding of template to the chemically modified polymers have been also investigated.

Development of an NMR metabolomics-based tool for selection of flaxseed varieties

Flaxseed is an important source of lignans and ω-3 fatty acids, compounds which present interest in human health with many applications in food industry. It is therefore necessary to precisely know the metabolite content in flaxseed. A metabolomic approach using NMR was developed to achieve this goal. Due to particular characteristics of flaxseed (high level in oil, high amount in mucilage, and integration of the phenolics into a macromolecule), the extraction procedure had first to be optimized using an experimental design, based on the extraction time, in a water bath or an ultrasound bath, alkaline treatment, defatting, and centrifugation temperature. This methodology was then applied to several flaxseed varieties classified in function of their content in ω-3 fatty acid. The main differences in semi-polar metabolites between these varieties concern compounds of the phenylpropanoid pathway. Hydroxycinnamic acid glucoside and lignan content increase when ω-3 fatty acid content decrease whereas flavonoid content increase in the same way of ω-3 fatty acids.

Kinetics of the incorporation of the main phenolic compounds into the lignan macromolecule during flaxseed development

The main flax lignan, secoisolariciresinol diglucoside, is stored in a macromolecule containing other ester-bound phenolic compounds. In this study, NMR and HPLC-UV analyses were performed on flaxseeds harvested at different developmental stages to identify and quantify the main phenolic compounds produced during seed development. Extraction was carried out with or without alkaline hydrolysis to determine if these molecules accumulate in the lignan macromolecule and/or in a free form. Monolignol glucosides accumulate in a free form up to 9.85mg/g dry matter at the early developmental stages. Hydroxycinnamic acid glucosides and flavonoid accumulate (up to 3.18 and 4.07mg/g dry matter, respectively) in the later developmental stages and are ester-bound in the lignan macromolecule. Secosiolariciresinol diglucoside accumulates (up to 28.65mg/g dry matter) in the later developmental stages in both forms, mainly ester-bound in the lignan macromolecule and slightly in a free form.