Diketogulonic acid

Structural formula
	Fischer projection
General
Surname	Diketogulonic acid
other names	L -diketogulonic acid; (4 S , 5 R ) -4,5,6-trihydroxy-2,3-dioxohexanoic acid ( IUPAC ); DKG;
Molecular formula	C 6 H 8 O 7 ; C 6 H 10 O 8 ( monohydrate ); C 6 H 12 O 9 ( dihydrate );
External identifiers / databases
PubChem	440390
ChemSpider	389343
Wikidata	Q1225282
properties
Molar mass	192.12 g · mol -1
Physical state	firmly
safety instructions
GHS hazard labeling ; no classification available
GHS hazard labeling ; no classification available
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

L - diketogulonic acid , also DKG for short, is a reaction product of dehydroascorbic acid .

Modifications

Similar to monosaccharides and ascorbic acid, diketogulonic acid can, depending on the conditions, be in open-chain and cyclic acetal form. The open-chain tautomer can also form geminal diols by adding water to the two keto groups . Both mono- and dihydrate have been proven here.

Reaction and importance

In aqueous solutions, L-diketogulonic acid is formed from dehydroascorbic acid ( DHA ) by saponification ( hydrolysis ) . Diketogulonic acid molecule tends to be broken down further into a multitude of products in aqueous solutions with in the neutral pH range. Erythroascorbic acid, L-lyxonic and L-xylonic acid, L-threosone (3,4-dihydroxy-2-oxo-butanal), L-threonic acid, oxalic acid and CO _{2 were} detected during decarboxylation. In addition to the oxidative degradation path, there is also a non-oxidative degradation of DKG, which leads to oxalic acid and L- erythrulose .

The breakdown of diketogulonic acid ( via 2,3-diketogulono-γ-lactone) is complicated. A distinction is made between oxidative degradation products (AE) and non-oxidative degradation products (F). So far, the following have been detected: L-threosone ( A ), L-lyxonic acid ( B ), L-xylonic acid ( C ), L-threonic acid ( D ), eyrthroascorbic acid ( E ), L-erythrulose ( F ), oxalic acid and CO ₂ (according to ).

In 2001 it could be proven that diketogulonic acid and two of its breakdown products (3,4-diketogulono-γ-lactone and 2,3-diketogulono-γ-lactone) protect proteins from egg yolk against oxidation by copper ions. The researchers attributed this to the presence of the enediol group in both γ-lactones, which are structurally and functionally similar to ascorbic acid. The 3,4-diketogulono-γ-lactone proved to be considerably more effective.

Since dehydroascorbic acid is often measured as a reaction product in the quantitative determination of vitamin C ( ascorbic acid ), the decay reaction described can falsify the measurement.

Individual evidence

↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
↑ H. Trommer, RHH Neubert: Ascorbic acid: new findings on the mode of action of a versatile, antioxidant vitamin , Institute for Pharmacy of the Martin Luther University Halle-Wittenberg .
↑ ^a ^b ^c ^d Nishikawa Y et al. (2001): Identification of 3,4-Dihydroxy-2-oxo-butanal (L-threosone) as an Intermediate Compound in Oxidative Degradation of Dehydro-L-ascorbic Acid and 2,3-Diketo-L-gulonic Acid in a Deuterium Oxide Phosphate Buffer . In: Bioscience, Biotechnology, and Biochemistry 65 (8), 1707-1712; PMID 11577707 ; doi: 10.1271 / bbb.65.1707 ; PDF (free full text access)
↑ Jung Ch. And Wells WW. (1998): Spontaneous conversion of L-dehydroascorbic acid to L-ascorbic acid and L-erythroascorbic acid . In: Archives of Biochemistry and Biophysics 355 (1): 9-14; PMID 9647661 .
↑ Kanfer J. et al. (1960): Formation of l-Lyxonic and l-Xylonic Acids from l-Ascorbic Acid in Rat Kidney. In: J. Biol. Chem. 235 ; 2518-2521; PDF (free full text access).
↑ Simpson G. and Ortwerth BJ (2000): The non-oxidative degradation of ascorbic acid at physiological conditions. In: Biochim Biophys Acta . 1501 (1): 12-24; PMID 10727845 .
↑ Li et al. (2001): Effects of 2,3-Diketo-L-Gulonic Acid on the Oxidation of Yolk Lipoprotein . In: Bioscience, Biotechnology, and Biochemistry 65 (3), 599-604; PMID 11330674 ; doi: 10.1271 / bbb.65.599 ; PDF (free full text access).

[NV-1] This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.

[2] H. Trommer, RHH Neubert: Ascorbic acid: new findings on the mode of action of a versatile, antioxidant vitamin , Institute for Pharmacy of the Martin Luther University Halle-Wittenberg .

[Yoko-3] Nishikawa Y et al. (2001): Identification of 3,4-Dihydroxy-2-oxo-butanal (L-threosone) as an Intermediate Compound in Oxidative Degradation of Dehydro-L-ascorbic Acid and 2,3-Diketo-L-gulonic Acid in a Deuterium Oxide Phosphate Buffer . In: Bioscience, Biotechnology, and Biochemistry 65 (8), 1707-1712; PMID 11577707 ; doi: 10.1271 / bbb.65.1707 ; PDF (free full text access)

[Jung-4] Jung Ch. And Wells WW. (1998): Spontaneous conversion of L-dehydroascorbic acid to L-ascorbic acid and L-erythroascorbic acid . In: Archives of Biochemistry and Biophysics 355 (1): 9-14; PMID 9647661 .

[Kanfer-5] Kanfer J. et al. (1960): Formation of l-Lyxonic and l-Xylonic Acids from l-Ascorbic Acid in Rat Kidney. In: J. Biol. Chem. 235 ; 2518-2521; PDF (free full text access).

[Simpson-6] Simpson G. and Ortwerth BJ (2000): The non-oxidative degradation of ascorbic acid at physiological conditions. In: Biochim Biophys Acta . 1501 (1): 12-24; PMID 10727845 .

[7] Li et al. (2001): Effects of 2,3-Diketo-L-Gulonic Acid on the Oxidation of Yolk Lipoprotein . In: Bioscience, Biotechnology, and Biochemistry 65 (3), 599-604; PMID 11330674 ; doi: 10.1271 / bbb.65.599 ; PDF (free full text access).