Depletion of the reduced glutathione level in the liver and production of the mutagens in the intestine in the mice inducing hepatoma by feeding on a high level dose of sorbic acid

Benzoate and Sorbate Salts: A Systematic Review of the Potential Hazards of These Invaluable Preservatives and the Expanding Spectrum of Clinical Uses for Sodium Benzoate

Sodium benzoate and potassium sorbate are extremely useful agents for food and beverage preservation, yet concerns remain over their complete safety. Benzoate can react with the ascorbic acid in drinks to produce the carcinogen benzene. A few children develop allergy to this additive while, as a competitive inhibitor of D-amino acid oxidase, benzoate can also influence neurotransmission and cognitive functioning. Model organism and cell culture studies have raised some issues. Benzoate has been found to exert teratogenic and neurotoxic effects on zebrafish embryos. In addition, benzoate and sorbate are reported to cause chromosome aberrations in cultured human lymphocytes; also to be potently mutagenic toward the mitochondrial DNA in aerobic yeast cells. Whether the substantial human consumption of these compounds could significantly increase levels of such damages in man is still unclear. There is no firm evidence that it is a risk factor in type 2 diabetes. The clinical administration of sodium benzoate is of proven benefit for many patients with urea cycle disorders, while recent studies indicate it may also be advantageous in the treatment of multiple sclerosis, schizophrenia, early-stage Alzheimer's disease and Parkinson's disease. Nevertheless, exposure to high amounts of this agent should be approached with caution, especially since it has the potential to generate a shortage of glycine which, in turn, can negatively influence brain neurochemistry. We discuss here how a small fraction of the population might be rendered-either through their genes or a chronic medical condition-particularly susceptible to any adverse effects of sodium benzoate.

4: Final Report on the Safety Assessment of Sorbic Acid and Potassium Sorbate

Sorbic acid is a straight-chain monocarboxylic acid used in cosmetic formulations as a preservative at concentrations up to 1.0%.

Sorbic acid and potassium sorbate were practically nontoxic to rats and mice in acute oral toxicity studies. In subchronic studies no significant adverse effects were observed in rats, mice, or dogs when 10% sorbic acid was included in the diet.

Sorbic acid and potassium sorbate at concentrations up to 10% were practically nonirritating to the rabbit eye. Both ingredients at concentrations up to 10% were at most only slightly irritating.

Sorbic acid and potassium sorbate have been tested for mutagenic effects using the Ames test, genetic recombination tests, reversion assays, rec assays, tests for chromosomal aberrations, sister chromatid exchanges, and gene mutations. Results have been both positive and negative.

Potassium sorbate at 0.1% in the diet or 0.3% in drinking water of rats for up to 100 weeks produced no neoplasms. In other chronic studies, no carcinogenic effect was demonstrated by sorbic acid in rats or mice fed diets containing up to 10% sorbic acid.

No teratogenic effects have been observed in pregnant mice and rats administered potassium sorbate.

In three repeat insult patch tests, sorbic acid had overall sensitization rates of 0, 0.33, and 0.8%. All of the subjects sensitized were inducted with 20% sorbic acid and challenged with 5% sorbic acid. Formulations containing up to 0.5% sorbic acid and or potassium sorbate were not significant primary or cumulative irritants and not sensitizers at this test concentration. A formulation containing 0.01% sorbic acid was not a photosensitizer.

On the basis of the available data, it is concluded that sorbic acid and potassium sorbate are safe as cosmetic ingredients in the present practices of use and concentration.

Effect of sorbic acid feeding on peroxisomes and sorboyl-CoA metabolizing enzymes in mouse liver. Selective induction of 2,4-dienoyl-CoA hydratase

On the basis of the finding that sorbic acid (SA)-induced hepatoma was correlated with the depletion of reduced glutathione (GSH) in mouse liver (Tsuchiya et al., Mutation Res 130: 267-262, 1984), the possible conversion of SA to a metabolite which is reactive with SH-compounds was studied. Sorboyl-CoA was hydrated and then reduced to 3-keto-4-hexenoyl-CoA by the combined actions of mitochondrial hydratase (crotonase) and L-3-hydroxyacyl-CoA dehydrogenase. Upon the addition of GSH or coenzyme A, 3-keto-4-hexenoyl-CoA was nonenzymatically converted to another 3-ketoacyl-CoA derivative, possibly a Michael type adduct, in a time- and concentration-dependent manner. Alternatively, sorboyl-CoA can be reduced by 2,4-dienoyl-CoA reductase and completely beta-oxidized without the generation of 3-keto-4-hexenoyl-CoA. Two-week feeding of mice of 15% SA caused a 2.0-fold induction of peroxisome beta-oxidation in the liver. SA caused a marked induction (3.6-fold) of hydratase toward sorboyl-CoA but a less pronounced induction (1.3-fold) of 2,4-dienoyl-CoA reductase, leading to about a 3-fold elevation in the hydratase: reductase ratio. The elevated ratio was sustained throughout the period of SA feeding up to 12 weeks. Thus, a large amount of SA could be converted to 3-keto-4-hexenoyl-CoA during this period. Oxidative stress caused by a depleted cellular SH-pool together with the induction of peroxisome proliferation by SA-feeding may implicate the mechanism by which non-mutagenic SA caused hepatoma.