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 concentration on betanin/betanidin chlorination efficiency in sodium hypochlorite and MPO systems was investigated. At pH 35, the yields of formed monochloro-betanin/-betanidin decrease dramatically at higher Cl- concentrations, indicating that generated Cl-2 is not the chlorinating agent in the presence of sodium hypochlorite. The intriguing low activity of Cl-2 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.