Although the enzyme catalase eats H2O2, it also reacts with numerous other substrates, including humans. An iron atom can be found in the catalase active site. Each of the four subunits that make up human catalase is composed of four domains: (1) an N-terminal arm that contains a terminal group of amino acids that are essential for the catalase reaction; (2) a β-barrel domain that contains eight β-barrels and six α-helical inserts arranged in an antiparallel manner, providing the protein core required for the enzyme's three-dimensional structure; (3) containing a heme-binding group of tyrosine residues; and (4) the α-helical domain, which is crucial for NADPH binding [1].

Absorption, Distribution and Excretion
By the oral route, parabens are rapidly absorbed, metabolized, and excreted. The metabolic reactions and conversions in mammals vary with the chain length of the ester, the animal species, route of administration, and quantity tested. The metabolism of parabens in humans appears to be most closely related to that of dogs. The rate of metabolite excretion appears to decrease with increasing molecular weight of the ester. /4-Hydroxybenzoates (Parabens)/
... Deposition of parabens in dogs. Urine recoveries ranged from 50-95% except for butyl ester for which recoveries were 40%. /It/... was concluded that esters are well absorbed and that hydrolysis of ester linkage and metabolic conjugation constitute chief route of elimination. Similar metabolic scheme ... in man. /Parabens/
The permeation of methylparaben, ethylparaben, propylparaben, and butylparaben through untreated and lipid-depleted excised guinea pig dorsal skin, and the effects of 3 penetration enhancers, N-dodecyl-2-pyrrolidone (lauryl pyrrolidone), ethyl alcohol (ethanol), and a mixture of menthol (l-menthol) and ethyl alcohol, on the permeation of the parabens were studied; the relationship between the permeability and octyl alcohol (n-octanol)/water partition coefficients of the parabens, and the effect of the penetration enhancers on the fluidity of the lipid bilayer of liposomes containing stratum corneum lipids were also examined. Permeability coefficients of the parabens correlated with their octyl alcohol/water partition coefficients in untreated guinea pig skin. In lipid-depleted guinea pig skin, permeability coefficients of the parabens increased and did not correlate with their octyl alcohol/water partition coefficients. The effect of the penetration enhancers on the permeation of the parabens was variable. The penetration enhancers increased the fluidity of liposome lipid bilayers.
After ethyl paraben is intravenously infused into the dog, unhydrolyzed ethyl paraben is found only in the brain. In liver, kidney, and muscle, it is immediately hydrolyzed to p-hydroxybenzoic acid. Six hours after oral administration of 1.0 g/kg to dogs, the peak plasma concentration of free and total ethyl paraben (427 and 648 ug/cu cm, respectively) is reached. After 48 hr, all ethyl paraben is completely eliminated.

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Metabolism / Metabolites
Yields p-hydroxybenzoic acid in pig and in Aspergillus. /from table/
/Paraben/ ... esters are well absorbed and hydrolysis of ester linkage and metabolic conjugation constitute chief route of elimination /in dogs/. Similar metabolic scheme was observed in man. /Paraben esters/
Urine from cats who had received (14)C-labeled ethyl-p-hydroxybenzoate, orally contained 2 major metabolites, p-hydroxyhippuric acid and free p-hydroxybenzoic acid.
In mice, rats, rabbits, pigs, or dogs, ethyl paraben is excreted in the urine as unchanged benzoate, p-hydroxybenzoic acid, p-hydroxyhippuric acid (p-hydroxybenzoylglycine), ester glucuronides, ether glucuronides, or ether sulfates.
For more Metabolism/Metabolites (Complete) data for ETHYLPARABEN (7 total), please visit the HSDB record page.
Ethyl-4-hydroxybenzoate has known human metabolites that include (2S,3S,4S,5R)-6-(4-ethoxycarbonylphenoxy)-3,4,5-trihydroxyoxane-2-carboxylic acid.

Toxicity Summary
IDENTIFICATION AND USE: Ethylparaben forms small colorless crystals, or white powder. Ethylparaben inhibits the growth of fungi and bacteria and is used as a preservative for pharmaceuticals, adhesives, and various cosmetic preparations. HUMAN EXPOSURE AND TOXICITY: Ethylparaben was a skin irritant in man. It gave no evidence of sensitizing potential in a human study. The paraben esters as a generic class are rare sensitizers when applied to the intact skin of man. Application to the damaged skin is a more common cause of sensitization. A methyl:ethyl:propylparaben mixture has been shown on oral administration to exacerbate pre-existing skin complaints. ANIMAL STUDIES: Ethylparaben was an eye irritant in rabbits. A low acute oral toxicity has been demonstrated for ethylparaben in laboratory animals. Limited long-term studies in rats have also indicated a low toxicity and have generated no evidence of carcinogenic activity. Ethylparaben in the diet produced cell proliferation in the forestomach of rats. No evidence of mutagenicity was reported in limited Ames Bacterial tests. Ethylparaben did increase chromosomal aberrations in a Chinese Hamster ovary cell assay, but similar effects were not seen in rats treated with ethylparaben. Fetal toxicity at maternally toxic dose levels occurred in female rats treated orally during pregnancy. Ethylparaben was nonteratogenic in rats. In one in vitro study, sperm were not viabile at concentrations as low as 8 mg/mL for Ethylparaben, but an in vivo study of 0.1% or 1.0% for Ethylparaben in the diet of mice reported no spermatotoxic effects.

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Interactions
The biological fates of ethyl paraben after the simultaneous administration with salicylic acid were different from those of ethyl paraben alone as reported in the previous reports. The excretion of unconjugated p-hydroxybenzoic acid, which is a hydrolyzed product of ethyl paraben, increased and those of p-hydroxyhippuric acid, glycine conjugate of p-hydroxybenzoic acid, and p-hydroxybenzoyl glucuronide, its ester type glucuronide, decreased. The blood concentration patterns were considerably different from those of ethyl paraben alone, especially the elimination of every metabolite was delayed. Pharmacokinetic analyses on the data of blood concentration were carried out and the results also show the interaction of salicylic acid on the biological fate of ethyl paraben.

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Non-Human Toxicity Values
LD50 Rat (female) oral 4.30 g/kg
LD50 Rat oral 11.0 g/kg
LD50 Guinea pig oral 2.0 g/kg /From table/
LD50 Rabbit oral 5.0 g/kg /From table/
For more Non-Human Toxicity Values (Complete) data for ETHYLPARABEN (9 total), please visit the HSDB record page.

[1]. Catalase, a remarkable enzyme: targeting the oldest antioxidant enzyme to find a new cancer treatment approach. Biol Chem. 2017 Sep 26;398(10):1095-1108.

Ethylparaben is an ethyl ester resulting from the formal condensation of the carboxy group of 4-hydroxybenzoic acid with ethanol, It has a role as an antimicrobial food preservative, an antifungal agent, a plant metabolite and a phytoestrogen. It is a paraben and an ethyl ester.
Ethylparaben is a Standardized Chemical Allergen. The physiologic effect of ethylparaben is by means of Increased Histamine Release, and Cell-mediated Immunity.
Ethylparaben has been reported in Aeschynanthus bracteatus, Inula salsoloides, and other organisms with data available.
Ethylparaben is found in alcoholic beverages. Ethylparaben is an antimicrobial agent, preservative. Ethylparaben is present in red wine, white wine and sake. Ethylparaben belongs to the family of Hydroxybenzoic Acid Derivatives. These are compounds containing an hydroxybenzoic acid (or a derivative), which is a benzene ring bearing a carboxylic acid.
Ethyl-4-hydroxybenzoate is a metabolite found in or produced by Saccharomyces cerevisiae.

C9H10O3

166.1739

166.062

9001-05-2

8434

Off-white to light yellow solid powder

1.2±0.1 g/cm3

297.5±0.0 °C at 760 mmHg

ofp-hydroxybenzoic acid isolated by acidification and not recrystallised: 213 °C to 217 °C, after vacuum drying in a sulphuric acid desiccator
117 °C
116 °C

120.3±12.6 °C

0.0±0.6 mmHg at 25°C

1.539

2.4

1

3

3

12

148

0

NUVBSKCKDOMJSU-UHFFFAOYSA-N

InChI=1S/C9H10O3/c1-2-12-9(11)7-3-5-8(10)6-4-7/h3-6,10H,2H2,1H3

ethyl 4-hydroxybenzoate

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

H2O : ~33.33 mg/mL
DMSO :< 1 mg/mL

Solubility in Formulation 1: 100 mg/mL (Infinity mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with sonication.

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 (Please use freshly prepared in vivo formulations for optimal results.)