Zbigniew Pietrzkowski

Antioxidant activity of betanidin: electrochemical study in aqueous media.

The antioxidative mechanism of action of betalains is of significant interest because these pigments are recently emerging as highly bio-active natural compounds with potential benefits to human health. Betanidin, the basic betacyanin, comprises the 5,6-dihydroxyl moiety, which results in its high antioxidant activity. Oxidation of betanidin by voltammetric techniques and chro matographic identification of the oxidation products with spectrophotometric and mass spectrometric detection (LC-DAD-MS/MS) were performed. Two main oxidation peaks for betanidin are observable at pH 3-5. These peaks become merged at higher pH, suggesting a different mechanism of oxidation at higher and lower pH values. The low oxidation potential of betanidin confirms its very strong reduction properties. The presence of two prominent oxidized products, 2-decarboxy-2,3-dehydrobetanidin and 2,17-bidecarboxy-2,3-dehydrobetanidin, indicates their generation through two reaction routes with two different quinonoid intermediates: dopachrome derivative and quinone methide. Both lead to the decarboxylative dehydrogenation of betanidin. Subsequent oxidation and rearrangement of the conjugated chromophoric system results in formation of 14,15-dehydrogenated derivatives.

Studies on Nonenzymatic Oxidation Mechanisms in Neobetanin, Betanin, and Decarboxylated Betanins

A comprehensive nonenzymatic oxidation mechanism in betanin plant pigment as well as its derivatives, 2-decarboxybetanin, 17-decarboxybetanin, 2,17-bidecarboxybetanin, and neobetanin, in the presence of ABTS cation radicals was investigated by LC-DAD-ESI-MS/MS. The main compounds formed during the first step of betanin and 2-decarboxybetanin oxidation are 2-decarboxy-2,3-dehydrobetanin and 2-decarboxyneobetanin, respectively. In contrast to betanin, the reaction mechanism for 2-decarboxybetanin includes more oxidation pathways. Parallel transformation of 2-decarboxybetanin quinone methide produces neoderivatives according to an alternative reaction that omits the presumably more stabile intermediate 2-decarboxy-2,3-dehydrobetanin. The main oxidation product after the first reaction step for both 17-decarboxybetanin and 2,17-bidecarboxybetanin is 2,17-decarboxy-2,3-dehydrobetanin. This product is formed through irreversible decarboxylation of the 17-decarboxybetanin quinone methide or by oxidation of 2,17-bidecarboxybetanin. Oxidation of neobetanin results primarily in a formation of 2-decarboxy-2,3-dehydroneobetanin by a decarboxylative transformation of the formed neobetanin quinone methide. The elucidated reaction scheme will be useful in interpretation of redox activities of betalains in biological tissues and food preparations.

Chlorination of betacyanins in several hypochlorous acid systems

This study presents a comparative evaluation of chlorination of betanin, betanidin, and neobetanin exposed to sodium hypochlorite and myeloperoxidase (MPO)/H2O2/Cl(-) systems. For betanin/betanidin, the chlorination takes place at the aglycone unit, but for neobetanin, no chlorinated products in the reaction mixtures can be detected. In the RP-HPLC system, monochloro-betanin/-betanidin were eluted earlier than their corresponding nonchlorinated substrates. An influence of Cl(-) concentration on betanin/betanidin chlorination efficiency in sodium hypochlorite and MPO systems was investigated. At pH 3-5, the yields of formed monochloro-betanin/-betanidin decrease dramatically at higher Cl(-) concentrations, indicating that generated Cl2 is not the chlorinating agent in the presence of sodium hypochlorite. The intriguing low activity of Cl2 in betanin/betanidin chlorination compared to HOCl and/or Cl2O can be explained by a special position of the attack by molecules of HOCl and/or Cl2O. In the MPO/H2O2/Cl(-) system, the highest efficiency of monochloro-betanin/-betanidin generation is observed at pH 5.

Short-term efficacy of calcium fructoborate on subjects with knee discomfort: a comparative, double-blind, placebo-controlled clinical study.

Calcium fructoborate (CFB) at a dose of 110 mg twice per day was previously reported to improve knee discomfort during the first 14 days of treatment. In this study, 60 participants with self-reported knee discomfort were randomized into two groups receiving CFB or placebo. Initial levels of knee discomfort were evaluated by Western Ontario and McMaster Universities Arthritis Index (WOMAC) and McGill Pain Questionnaire (MPQ) scores at the beginning of the study and also at 7 and 14 days after treatment. Results showed that supplementation with CFB significantly improved knee discomfort in the study subjects; significant reductions of mean within-subject change in WOMAC and MPQ scores were observed for the CFB group compared to the placebo group at both 7 and 14 days after treatment. Estimated treatment differences for the MPQ score were −5.8 (P=0.0009) and −8.9 (P<0.0001) at Day 7 and 14, respectively. Estimated differences for the WOMAC score were −5.3 (P=0.06) and −13.73 (P<0.0001) at Day 7 and 14, respectively. Negative values indicate greater reductions in reported discomfort. On both Day 7 and Day 14, the trend was toward greater improvement in the CFB group. The placebo group did not exhibit any change in the WOMAC and MPQ scores. In conclusion, supplementation with 110 mg CFB twice per day was associated with improving knee discomfort during the 2 weeks of intake.