Reductones, detection

In the cysteine/glucose model experiments glucose reduc-tone, acetylformoin, furaneol and cyclotene were detected as major constituents indicating that the 1-deoxy-osone route is operative at pH-values o 5 to 7. As main component we identified by MS, IR- and H-NMR-spectroscopy 4-hydroxy-2,5-dimethyl-3(2H)thiophenone. Obviously this compound is less reactive than the corresponding norfuraneol derivative. Thiofuraneol is also formed from glucose/reductone, acetylformoin and furaneol as demonstrated in model experiments. Surprisingly, it is not formed in cysteine/rhamnose experiments, where furaneol is a major compound. In addition 2-acetyl-4-thiolanone and 5-hydroxymethyl-2-methyl-3-thiolanone were identified for the first time as cysteine specific products. 

The procedure of Chen ef al. (C7) separated the ascorbic acid on paper using n-butanol or phenol saturated with oxalic acid to retard decomposition. A preliminary preparative separation could be used to concentrate the sample. Qualitative identification was made from the R/ of the spots located by spraying with 0.08 % 2,6-dichlorophenolindophe-nol, and quantitative analysis by elution with oxalic acid and titration with the same dye. Recoveries from urine and cress seedlings were 85 % or more at even the lowest concentrations tested (0.5 mg/ml), and the method could detect 1-2 fig ascorbic acid per cm of paper. The method clearly separated L-ascorbic acid and D-araboascorbic acid as well as hydroxytetronic acid, reductinic acid, and reductone. 

Wahl, R. Detection and separation of (triose) Reductone, mesoxaldialdehyde and hydroxypyruvic acid during sugar determination in Hue-cured tobaccos Tabak-Forschung (1957) (19) 42-A5. 

As shown in Table III no radicals could be detected clearly demonstrating that the CROSSPY formation was still in the induction period. In order to check the influence of reductones on radical formation, this ftiermally pre-treated mixture was incubated in the presence of ascorbic acid at room temperature. Analysis of the mixture by EPR spectroscopy revealed that instanftmeously after reductone addition the radical cation was generated (Table III). To investigate the effectivity of carbohydrate-derived reductones in CROSSPY formation, in comparative experiments, acetylformoin as well as methylene reductinic acid, both well-known to be formed during thermal treatment of hexoses (19), were added to the thermally pre-treated mixture. Both the Maillard reaction products were found to rapidly induce radical formation, however, in somewhat lower effectivity when compared to ascorbic acid (Table III). 

On the other hand. Chance (1952a) claimed an essential role for manganous ions, as indicated by the reported velocity constants reproduced in Table III. Under his conditions hydrogen peroxide could only partially replace the manganese. In the reaction with triose reductone, Yamazaki et al. (1956) show that manganese only produces an appreciable activation at alkaline pH values, where the peroxidase alone is almost inactive. They claim that the only extra component essential for oxidatic activity is hydrogen peroxide, a deficiency of which can be detected by an initial lag in substrate disappearance. 

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