Two oxidation pathways of bioactive flavonol rhamnazin under ambient conditions

• The oxidation mechanism of rhamnazin has not been solved yet.
• Rhamnazin decomposes in solution during minutes handled in the presence of air.
• The main oxidation product of rhamnazin was identified even if it is not stable.
• Two parallel oxidation mechanisms of rhamnazin in air were determined.

Two pathways of the oxidation mechanism of rhamnazin under ambient conditions are proposed. The redox potential of rhamnazin strongly depends on the presence of dissociation forms in solution. In situ spectroelectrochemistry and identification of degradation products by HPLC-DAD and HPLC–ESI-MS/MS confirmed the presence of fast subsequent chemical reactions following the electron transfer. As demonstrated, strict anaerobic conditions have to be preserved in studies of antioxidant properties and of its pharmacological efficiency. In the absence of oxygen, 2,4-dihydroxy-2-(4′-hydroxy-3′-methoxybenzoyl)-6-methoxy-benzofuran-3(2H)-one was identified as the only oxidation product.

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