An Approach to the Characterization of Betanine Oxidation Catalyzed by Horseradish Peroxidase

Abstract

Horseradish peroxidase (HRP, EC 1.1.11.7) catalyzed oxidation of betanine is complex, as judged by the shape of the consecutive absorption spectra of the reaction medium. Graphic analysis of these spectra by a matricial test revealed the presence of at least three kinetically related absorbent species in the reaction mixture. Analysis by HPLC confirmed the presence of several reaction products. During the course of the reaction, a red intermediate and several yellow products, presumably of a polymeric nature, are generated, betalamic acid being one of the final products. Even in the absence of enzyme, the reaction, once initiated, continued again, yielding betalamic acid as a final product, which is formed as both substrate and intermediate product disappear. The chemical nature of the intermediate product and the possible reaction mechanism are discussed. Keywords: Beta vulgaris; betanine oxidation; peroxidase; red beet

Betanin inhibits the myeloperoxidase/nitrite-induced oxidation of human low-density lipoproteins

“…Oxidation products of betanin by MPO are not known. Products from the reaction between betanin and horseradish peroxidase have been described as stable phenoxyl radicals and betalamic acid [43], however, we failed to have any spectral evidence of such compounds in our system. It is tempting to speculate that a rapid reaction of betanin and/or MPO-oxidised betanin with NO z 2 led to the accumulation of end-products that do not exhibit a characteristic absorbance spectrum.…”

Correlation between antiradical activity and stability of betanine from Beta vulgaris L roots under different pH, temperature and light conditions

“…Thus, when betanine was incubated in basic solutions at 75 °C (Fig 1), the shoulder was already present 15 min after initiating the treatment, and it became the maximum peak in the absorption spectrum after 90 min (data not shown). The degradation of betanine leads to the formation of CDG and BA as products15, 19 (Scheme ). It is known that the amount of betanine that can be regenerated after heating is a function of both the pH and the presence of BA and CDG in the reaction media 3.…”

“…These were separated by elution with 50 m M phosphate buffer, pH 7.0, through a Sephadex G‐25 column at a flow rate of 1 ml min −1 as described by Escribano et al 8 The eluate was collected in 2 ml fractions, and betacyanin concentrations (as betanine) were calculated using ϵ 1% = 1120 at 537 nm 18. High‐pressure liquid chromatography (HPLC) analysis19 revealed that betanine was the only component of the betacyanin fractions. The chromatograms were run with methanol/water mobile phase, and detailed operating conditions for analysis were as described by Martinez‐Parra and Muñoz 19…”

“…High‐pressure liquid chromatography (HPLC) analysis19 revealed that betanine was the only component of the betacyanin fractions. The chromatograms were run with methanol/water mobile phase, and detailed operating conditions for analysis were as described by Martinez‐Parra and Muñoz 19…”

Dynamics of Interfacial Electron Transfer from Betanin to Nanocrystalline TiO2: The Pursuit of Two-Electron Injection

“…18−20 In ref 15, three oxidations of Bt were detected at 0.62, 0.84, and 1.2 V NHE, whereas two oxidations of In were observed at 0.84 and 1.2 V. This indicates that the first oxidation of Bt involves the aromatic ring or the sugar group. 21 An early study by Martı́nez-Parra and Munõz 13 used horseradish peroxidase to oxidize betanin and found an oxidation intermediate with an absorption maximum similar to that of betanin (∼530 nm) and a yellow final oxidation product (λ max = 446 nm), which they assigned to betalamic acid. However, more recent studies assign λ max of betalamic acid to be about 420 nm.…”