Protection by glutathione and propyl gallate on the impaired in vitro amino acid incorporation into liver microsomal protein of CCL 4 -poisoned rats

2 Final Report on the Safety Assessment of Propyl Gallate

Propyl Gallate acid is used as an antioxidant in cosmetic products at concentrations normally less than 0.1 percent. Propyl Gallate is absorbed when ingested, methylated, conjugated, and excreted in the urine. Acute animal toxicity studies indicate that Propyl Gallate is slightly toxic when ingested and practically nontoxic when applied to the skin. Numerous chronic oral toxicity studies indicate that Propyl Gallate at concentrations up to 5 percent is practically nontoxic to rats, mice, dogs, and guinea pigs.

Propyl Gallate is nonirritating to human skin at concentrations up to 10 percent; however, it is sensitizing at this and higher concentrations. Propyl Gallate was nonphototoxic. It is concluded that Propyl Gallate is safe as a cosmetic ingredient at concentrations not exceeding 1 percent.

Final report on the amended safety assessment of Propyl Gallate

Propyl Gallate is the n-propyl ester of gallic acid (3,4,5-trihydroxybenzoic acid). It is soluble in ethanol, ethyl ether, oil, lard, and aqueous solutions of polyethylene glycol (PEG) ethers of cetyl alcohol, but only slightly soluble in water. Propyl Gallate currently is used as an antioxidant in a reported 167 cosmetic products at maximum concentrations of 0.1%. Propyl Gallate is a generally recognized as safe (GRAS) antioxidant to protect fats, oils, and fat-containing food from rancidity that results from the formation of peroxides. Data on dermal absorption are not available, but Propyl Gallate is absorbed when ingested, then methylated, conjugated, and excreted in the urine. The biological activity of Propyl Gallate is consistent with its free-radical scavenging ability, with effects that include antimicrobial activity, enzyme inhibition, inhibition of biosynthetic processes, inhibition of the formation of nitrosamines, anesthesia, inhibition of neuromuscular response to chemicals, ionizing/ultraviolet (UV) radiation protection, chemoprotection, antimutagenesis, anticarcinogenesis and antitumorigenesis, antiteratogenesis, and anticariogenesis. Animal toxicity studies indicate that Propyl Gallate was slightly toxic when ingested, but no systemic effects were noted with dermal application. Propyl Gallate is a strong sensitizer when tested intradermally, less sensitizing when tested topically, and nonsensitizing topically at 0.1% in one study. In a second study, Propyl Gallate (15 mg dissolved in 8 ml vehicle) was sensitizing to guinea pigs. Acute eye irritation tests conducted on nine cosmetic formulations, each containing less than 1% Propyl Gallate, were negative. A phototoxicity study conducted on a cosmetic formulation containing 0.003% Propyl Gallate determined that the product was not phototoxic to guinea pigs. In one study, female rats fed 0.5 g Propyl Gallate had substantially increased fetal resorption rates when compared to controls, but in four other studies, Propyl Gallate at doses up to 2.04 g/kg was nonteratogenic in rats, rabbits, mice, and hamsters. In clinical cumulative irritancy tests, Propyl Gallate was nonirritating at concentrations up to 10%. Patch tests at concentrations less than 1% yielded positive elicitation responses. Repeat-insult patch tests using cosmetic formulations with 0.003% Propyl Gallate produced no irritation or sensitization. Propyl Gallate at a concentration of 10% in alcohol was nonphototoxic in 25 subjects. Cosmetic formulations, each containing 0.003% Propyl Gallate, produced no signs of photosensitization or phototoxicity in a total of 371 subjects. Although Propyl Gallate is not a skin irritant in clinical tests, the available data demonstrate that it is a skin sensitizer and that it may be a sensitizer at lower concentrations than originally thought, i.e., at concentrations less than 1%. In actual practice, cosmetic formulations contain Propyl Gallate at concentrations up to 0.1% and usage has increased over the past 20 years. In spite of the increased exposure associated with increased use, it is the clinical experience of the Panel that the use of Propyl Gallate in cosmetics has not resulted in sensitization reactions. Therefore, the Panel believes that a concentration limitation of 0.1% in cosmetics is necessary (given the evidence of sensitization at concentrations less than 1%) and sufficient (given that current products are not producing adverse reactions).

Three models of free radical-induced cell injury

Three models of free radical-induced cell injury are presented in this review. Each model is described by the mechanism of action of few prototype toxic molecules. Carbon tetrachloride and monobromotrichloromethane were selected as model molecules for alkylating agents that do not induce GSH depletion. Bromobenzene and allyl alcohol were selected as prototypes of GSH depleting agents. Paraquat and menadione were presented as prototypes of redox cycling compounds. All these groups of toxins are converted, during their intracellular metabolism, to active species which can be radical species or electrophilic intermediates. In most cases the activation is catalyzed by the microsomal mixed function oxidase system, while in other cases (e.g. allyl alcohol) cytosolic enzymes are responsible for the activation. Radical species can bind covalently to cellular macromolecules and can promote lipid peroxidation in cellular membranes. Of course both phenomena produce cell damage as in the case of CCl4 or BrCCl3 intoxication. However, the covalent binding is likely to produce damage at the molecular site where it occurs; lipid peroxidation, on the other hand, besides causing loss of membrane structure, also gives rise to toxic products such as 4-hydroxyalkenals and other aldehydes which in principle can move from the site of origin and produce effects at distant sites. Electrophilic intermediates readily reacts with cellular nucleophiles, primarily with GSH. The result is a severe GSH depletion as in the case of bromobenzene or allyl alcohol intoxication. When the depletion reaches some threshold values lipid peroxidation develops abruptly and in an extensive way. This event is accompanied by cellular death. The reason for which lipid peroxidation develops in a cell severely depleted of GSH remains to be clarified. Probably the loss of the defense systems against a constitutive oxidative stress is not compatible with cellular life. Some free radicals generated by one-electron reduction can react with oxygen to give superoxide anions which can be converted to other more dangerous reactive oxygen species. This is the case of paraquat and menadione. Damage to cellular macromolecules is due to the direct action of these oxygen radicals and, at least in the menadione-induced cytotoxicity, lipid peroxidation is not involved. All these initial events affect the protein sulfhydryl groups in the membranes. Since some protein thiols are essential components of the molecular arrangement responsible for the Ca2+ transport across cellular membranes, loss of such thiols can affect the calcium sequestration activity of subcellular compartments, that is the capacity of mitochondria and microsomes to regulate the cytosolic calcium level.(ABSTRACT TRUNCATED AT 400 WORDS)