Endogenous Metabolite; Microbial Metabolite

Solid complexes of D-galacturonic acid (GalA) with cobalt(II), copper(II), nickel(II) and oxovanadium(IV) (1-4) were prepared and characterised. The metal-to-ligand molar ratio was 1:2 for complexes 1-3 and 1:1 for complex 4. The alpha- and beta-anomers of GalA were detected in all the complexes in solid state and in solutions. An addition of small amounts of the paramagnetic complexes to the D2O solution of pure ligand led to NMR line broadening of some 1H and 13C nuclei. This broadening was sensitive to the anomeric state of GalA in the case of complexes 1 and 4. NMR and vibrational spectroscopic data indicate the formation of carboxylate complexes of all the cations, while noncarboxylic oxygens are also involved into the metal bonding in some cases. VCD spectra of complexes 1-4 in D2O and Me2SO-d6 solutions confirm that GalA carboxylic group may participate in the formation of optically active species around the metal cation. Possible ways of GalA coordination by metal cations of this study were proposed and discussed. [1]

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Past investigations have shown high browning potential during the caramelization of sugar acids in comparison to reducing sugars. However, no approaches to elucidate the chemical mechanisms have been made. Therefore, this study aims to clarify the reasons for the high browning potential by measuring the mutarotation velocity and the elimination of CO2 during the heat treatment of uronic acids. Performed polarimetric experiments show that the mutarotation velocity of d-galacturonic acid exceeds that of d-galactose by a factor of nearly 4.5. However, the ring opening velocity is not the only parameter that differs between the two carbohydrate structures. Measurements of the release of CO2 of heated d-galacturonic acid at 60 °C show a steady increase, and after 48 h, 6% of degraded d-galacturonic acid has eliminated CO2. CO2 release was also found during the heating of pectin, indicating a decarboxylation reaction during thermal degradation. One of the degradation reactions postulated for the release of CO2 leads to α-ketoglutaraldehyde, which is responsible for the formation of several chromophoric substances.[2]

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This paper describes a convenient and efficient synthesis of new complexing surfactants from d-galacturonic acid and n-octanol as renewable raw materials in a two-step sequence. In the first step, simultaneous O-glycosidation-esterification under Fischer conditions was achieved. The anomeric ratio of the products was studied based on the main experimental parameters and the activation mode (thermal or microwave). In the second step, aminolysis of the n-octyl ester was achieved with various functionalized primary amines under standard thermal or microwave activation. The physico-chemical properties of these new amphiphilic ligands were measured and these compounds were found to exhibit interesting surface properties. Complexing abilities of one uronamide ligand functionalized with a pyridine moiety toward Cu(II) ions was investigated in solution by EPR titrations. A solid compound was also synthesized and characterized, its relative structure was deduced from spectroscopic data. [3]

[1]. The complexation of metal cations by D-galacturonic acid: a spectroscopic study. Carbohydr Res. 2004 Oct 4;339(14):2391-405.
[2]. Influence of the Carboxylic Function on the Degradation of d-Galacturonic Acid and Its Polymers. J Agric Food Chem. 2021 Aug 18;69(32):9376-9382.
[3]. Synthesis, physico-chemical properties and complexing abilities of new amphiphilic ligands from D-galacturonic acid. Carbohydr Res. 2010 Apr 19;345(6):731-9.

It is valid for both α- and β-anomeric models of complex 4 that the hydrogen and carbon atoms located close by at least one of the cations demonstrate specific broadening of their NMR resonances. In addition, in both cases the oxovanadium(IV) cations are in distorted tetragonal pyramidal configuration that is in agreement with results of electronic and vibrational spectroscopy. [1]

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The investigations carried out on d-galacturonic acid and its polymers in the course of this scientific work indicate that uronic acids in all their forms have an influence on the processing and storage of plant-based foods. The results obtained at the lowest temperatures and under accelerating storage conditions clearly show that degradation already takes place during storage and can, thus, negatively affect the quality of groceries. On the one hand, this degradation of pectin can lead to a reduced ability to form gels, as decarboxylation promotes the depolymerization of the pectin chain. On the other hand, undesirable color formation can occur, which even enhances during extended heat treatment during processing. For this reason, it is imperative to conduct further studies under near-real conditions with regard to the degradation of d-galacturonic acid and its polymers in food. [2]

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The synthesis of original n-octyl (galactosid)uronamides with several heteroatoms on the amide moiety has been achieved in a two-step sequence: esterification–O-glycosidation and aminolysis. For the first step, a detailed study of the experimental conditions (equivalents of alcohol, heating time and source, acid catalyst) has shown that, in each case, a mixture of anomers is obtained with the β-furanose as the major reaction product. A comparison of the results obtained using a thermostated oil-bath or microwave irradiation (monomode reactor) revealed that the microwave-assisted reactions dramatically improved the transformation in terms of reaction time (10 min vs 48 h), yield (>90% vs 80%), anomer ratio and purity. Solvent-free aminolysis of the esters was then performed with the major β-furanose compound, using thermal or microwave activation, to afford the corresponding galacturonamides in good yields. n-Octyl (galactosid)uronamides have been found to be good surface-active surfactants in spite of a C8 alkyl chain. These adsorption properties are very slightly influenced by the anomeric configuration and by the nature of the complexing amino group which favors self-assembly of the surfactants. The n-octyl (galactosid)uronamides appear particularly interesting as chelating surfactants provided that the complexes remain soluble in water. The complexation reaction of one uronamide ligand functionalized with a pyridine moiety 2a toward copper ions was investigated in methanol/water media. Results show that the pyridine moiety allows the deprotonation of the amidic nitrogen atom and the binding of metal ions via the formation of a five-member chelate ring. Our results reveal the formation of mononuclear copper complexes species between pH 2.5 and pH 6 and of dinuclear species at more alkaline media. Finally, these results demonstrate that the prepared n-octyl galacturonamides can be used as complexing agents for inorganic cations as pure anomers or as mixtures of anomers and could act as ion carriers. The complexing abilities of the other GalA-derived ligands 3a–6a toward cations, especially Cu2+, and the physico-chemical properties of these Cu(II) complexes are currently underway and will be reported in due course.[3]

C6H12O8

212.15

212.053

91510-62-2

685-73-4; 14984-39-5

2724373

White to off-white solid powder

495.2ºC at 760 mmHg

164-165ºC

211.1ºC

52.5 ° (C=10, H2O)

6

8

1

14

205

4

[C@@H]1([C@H]([C@H](OC([C@@H]1O)O)C(=O)O)O)O.O

BGHPCEJXDOGRGW-KSSASCOMSA-N

InChI=1S/C6H10O7.H2O/c7-1-2(8)4(5(10)11)13-6(12)3(1)9;/h1-4,6-9,12H,(H,10,11);1H2/t1-,2+,3+,4-,6?;/m0./s1

(2S,3R,4S,5R)-3,4,5,6-tetrahydroxyoxane-2-carboxylic acid;hydrate

D-(+)-Galacturonic acid monohydrate; ALPHA-D-GALACTURONIC ACID HYDRATE; (2S,3R,4S,5R)-3,4,5,6-tetrahydroxyoxane-2-carboxylic acid;hydrate; D-GALACTURONIC ACID HYDRATE; MFCD00071585; 685-73-4 (anhydrous);

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

H2O: 125 mg/mL (589.21 mM)

Solubility in Formulation 1: 100 mg/mL (471.36 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with sonication.

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 (Please use freshly prepared in vivo formulations for optimal results.)