A method for preparing a polycarboxylic composition, includes a stage in which a monosaccharide composition undergoes an electrochemical oxidation treatment carried out in the absence of sodium hypochlorite and in the presence of a) an amine oxide and b) a carbon-based anode. Preferably, the anode is selected from the group comprising carbon felt and granular active carbon. The electrochemical oxidation treatment can be carried out advantageously at a pH, preferably of between 11.5 and 14. The method makes it possible to obtain novel products, especially 2-carboxy-2, 3, 4-trihydroxypentane-dioicious acid, the salts and derivatives thereof.