A skin treatment preparation including carriers, a medicinal vector encapsulating a plant extract (Cucumis melo protein extract) rich in reductase, catalase and superoxide dismutase is characterized in that the medicinal vector, of nanospheres, represents 1 to 20 wt. % of the weight of the preparation; and the encapsulated plant extract represents 5 to 15 wt. % of the weight of the nanospheres; and the encapsulated plant extract may have the following enzymatic concentrations: reductase between 100 and 1000 IU, catalase between 100 and 1000 IU, and superoxide dismutase between 500 and 5000 IU. The preparation is useful for limiting depigmentation and reducing inflammatory front in vilitigo pathology and possible repigmentation.