The present work studies the ability of a germinated seeds extract (alfalfa, radish, wheat, soy) to influence cell respiration of skin fibroblasts and the respiratory activity of sheep liver isolated mitochondria, and the cytotoxicity of the product on cultured skin fibroblasts. The content of free and total amino acids present in this extract was determined. Aspartic acid represented 37.52% of free amino acids in the extract, but 48.07% glutamic acid was found when total amino acids obtained by acid hydrolysis were quantified. The extract contains more than 6.5% free serine, glutamic acid and alanine. Arginine, serine, aspartic acid and threonine are the other amino acids that represent more than 4.5% total amino acids. Respiration of sheep liver mitochondria and human skin fibroblasts (Foreskin ATCC CRL-1635) was checked polarographically. The results obtained show the ability of this extract to stimulate cellular respiration of both in vitro models, but the effect is more marked on cell cultured fibroblasts, and its dose dependency. The role of acidic amino acids, aspartic and glutamic acids, on the increase of oxygen consumption by mitochonria is suggested. Cytotoxicity of the germinated seeds extract was tested by the assessment of the viability, the morphological changes and the proliferation of cell cultured human skin fibroblasts. It has been shown that germinated seeds extract are non-toxic to cell cultures at doses of up to 10 mg mL(-1); neither morphological changes nor membrane integrity alterations or changes in cell proliferation were observed.