A number of natural dye extracts were obtained from vegetal and fungal sources. Red grapes marc is an important raw material for producing red food colorants. White grapes marc and onion peels could be used for extracting yellow flavonoids. The extraction methodology was established in accordance to the nature of the pigments and that of the biologic material. The study includes the analysis of electro-chemical properties of these natural and other synthetic alimentary azo dyes. Generally, the natural food colorants could be reduced or oxidized easier than the synthetic ago dyes.