Ecotoxicological effects of the antioxidant additive propyl gallate in five aquatic systems

Propyl gallate is an antioxidant widely used in foods, cosmetics and pharmaceuticals. The occurrence and fate of additives in the aquatic environment is an emerging issue in environmental chemistry. To date, there is little available information about the adverse effects of propyl gallate on aquatic organisms. Therefore, the toxic effects were investigated, using five model systems from four trophic levels. The most sensitive system was the hepatoma fish cell line PLHC-1 according to total protein content, with an EC50 of 10 μM and a NOAEL of 1 μM at 72 h, followed by the immobilization of Daphnia magna, the inhibition of bioluminescence of Vibrio fischeri, the salmonid fish cell line RTG-2 and the inhibition of the growth of Chlorella vulgaris. Although protein content, neutral red uptake, methylthiazol metabolization and acetylcholinesterase activity were reduced in PLHC-1 cells, stimulations were observed for lysosomal function, succinate dehydrogenase, glucose-6-phosphate dehydrogenase and ethoxyresorufin-O-deethylase activities. No changes were observed in metallothionein levels. The main morphological observations were the loss of cells and the induction of cell death mainly by necrosis but also by apoptosis. The protective and toxic effects of propyl gallate were evaluated. General antioxidants and calcium chelators did not modify the toxicity of propyl gallate, but an iron-dependent lipid peroxidation inhibitor gave 22% protection. The results also suggest that propyl gallate cytotoxicity is dependent on glutathione levels, which were modulated by malic acid diethyl ester and 2-oxothiazolidine-4-carboxylic acid. According to the results, propyl gallate should be classified as toxic to aquatic organisms.