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.

For the α- and β-anomer models of complex 4, both hydrogen and carbon atoms near at least one cation exhibit specific NMR peak broadening. In addition, the vanadium(IV) cation in both cases exhibits a distorted tetragonal pyramidal configuration, consistent with the results of electronic and vibrational spectroscopy. [1]

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This study on d-galacturonic acid and its polymers shows that all forms of uronic acid affect the processing and storage of plant-based foods. The results obtained under minimum temperature and accelerated storage conditions clearly indicate that degradation occurs during storage and has a negative impact on food quality. On the one hand, this degradation of pectin leads to a decrease in gel-forming ability because decarboxylation promotes the depolymerization of pectin chains. On the other hand, undesirable color formation may occur, especially after prolonged heat treatment during processing. Therefore, further research is needed on the degradation of D-galacturonic acid and its polymers in food under near-realistic conditions. [2]

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Novel n-octyl (galactoside) uronic amides with multiple heteroatoms in the amide moiety have been synthesized via a two-step reaction: esterification-O-glycosylation and ammonolysis. For the first step, detailed studies of the experimental conditions (equivalent alcohol, heating time, heat source, acid catalyst) showed that a mixture of isomers was obtained under each condition, with β-furanose being the major product. Comparison of results obtained using a constant-temperature oil bath or microwave irradiation (single-mode reactor) revealed that microwave-assisted reaction significantly improved conversion in terms of reaction time (10 min vs 48 h), yield (>90% vs 80%), isomer ratio, and purity. Subsequently, solventless ammonolysis of the major β-furanose compound was performed using thermal or microwave activation to obtain the corresponding galactouronic amides in good yield. Despite having a C8 alkyl chain, n-octyl (galactoside) uronic amides have been found to be good surface-active surfactants. These adsorption properties are minimally affected by isomer configuration and the properties of the complexed amino group, which facilitates surfactant self-assembly. Octyl (galactoside) aldehyde amides show particular promise as chelating surfactants, provided the complex remains water-soluble. In a methanol/water medium, we investigated the complexation reaction of a pyridine-functionalized ureaamide ligand 2a with copper ions. The results showed that the pyridine group deprotonates the amide nitrogen atom and binds to metal ions by forming a five-membered chelate ring. Our findings revealed the formation of mononuclear copper complexes between pH 2.5 and pH 6, and binuclear complexes in more alkaline media. Finally, these results indicate that the prepared octyl galactoside amide can serve as a complexing agent for inorganic cations, existing as a pure isomer or a mixture of isomers, and can also act as an ion carrier. The complexing ability of other GalA-derived ligands 3a–6a to cations (especially Cu2+) and the physicochemical properties of these Cu(II) complexes are currently under investigation, and the results will be reported separately. [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.)