The primary target of catalase is hydrogen peroxide (H₂O₂), a reactive oxygen species generated during normal metabolic processes. By catalyzing the dismutation of H₂O₂ into water and oxygen, catalase protects cells from oxidative stress and maintains redox homeostasis. Its activity is essential for preventing the accumulation of H₂O₂, which can cause damage to proteins, lipids, and nucleic acids. In addition to its catalytic function, catalase has been studied for its role in modulating gene expression and apoptosis in response to oxidative stress. In tumors, the expression and localization of catalase are markedly altered, linking it to cancer development and progression.

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].
In vitro, catalase is widely used as a research tool to study the role of reactive oxygen species in cellular processes. It is commonly added to cell culture media to scavenge H₂O₂ and protect cells from oxidative damage. Catalase activity can be measured spectrophotometrically by monitoring the decrease in absorbance at 240 nm as H₂O₂ is degraded. In biochemical assays, catalase is used to confirm that observed effects are mediated by H₂O₂, as the addition of catalase should reverse the effects of exogenously added H₂O₂. Its efficacy in protecting proteins, lipids, and nucleic acids from oxidative damage has been well documented in numerous in vitro studies.

In vivo, catalase has been investigated for its therapeutic potential in diseases involving oxidative stress, including ischemia-reperfusion injury, neurodegenerative disorders, and certain cancers. Due to its large size and poor cellular penetration, catalase is often delivered via gene therapy or nanoparticle-based delivery systems. In animal models, catalase gene therapy has shown protective effects against oxidative damage in various tissues. Additionally, catalase mimetics and combination antioxidant therapies are being explored in clinical trials for their neuroprotective effects against amyloid-beta toxicity in Alzheimer's disease.

In vitro enzyme activity assays for catalase are performed by measuring the rate of hydrogen peroxide decomposition. The assay is typically conducted in a UV-transparent cuvette containing a phosphate buffer (pH 7.0) and a known concentration of H₂O₂. The reaction is initiated by the addition of catalase, and the decrease in absorbance at 240 nm is monitored over time. One unit of catalase activity is defined as the amount of enzyme that decomposes 1 μmol of H₂O₂ per minute at 25°C and pH 7.0. The specific activity of the enzyme is calculated as units per milligram of protein.

In vitro cellular experiments with catalase involve treating cells with the enzyme to study its protective effects against oxidative stress. Cells are pre-incubated with catalase or exposed to it simultaneously with an oxidative stressor such as H₂O₂. Cell viability is then assessed using MTT or LDH release assays. Intracellular ROS levels can be measured using fluorescent probes such as DCFH-DA. To confirm that the protective effect is due to catalase activity, heat-inactivated catalase is used as a negative control. These experiments are essential for understanding the role of catalase in cellular defense mechanisms against oxidative damage.

In vivo animal studies for catalase typically involve models of oxidative stress-related diseases. Catalase is administered via intravenous injection, often encapsulated in nanoparticles or liposomes to improve its bioavailability and cellular uptake. Alternatively, catalase gene therapy is employed using viral or non-viral vectors to achieve sustained expression of the enzyme in target tissues. The efficacy of the treatment is evaluated by measuring markers of oxidative stress, such as malondialdehyde (MDA) and glutathione (GSH) levels, in tissues. Histopathological analysis is also performed to assess tissue damage and the extent of protection conferred by catalase.

Absorption, Distribution and Excretion
Following oral administration, parabens are rapidly absorbed, metabolized, and excreted. Metabolic responses and transformations in mammals vary depending on ester chain length, animal species, route of administration, and test dose. The metabolism of parabens in humans appears to be most similar to that in dogs. The excretion rate of metabolites appears to decrease with increasing ester molecular weight. /4-Hydroxybenzoate (parabens)/ …Deposition of parabens in dogs. Except for butyl ester, which had a recovery rate of 40%, the urinary recovery rates of other esters ranged from 50% to 95%. /It/ …It is concluded that esters are well absorbed, and ester bond hydrolysis and metabolic conjugation are the main elimination pathways. Similar metabolic mechanisms…in humans. Parabens
This study investigated the permeation of methylparaben, ethylparaben, propylparaben, and butylparaben in untreated and lipid-depleted isolated guinea pig dorsal skin, and the effects of three permeation enhancers—N-dodecyl-2-pyrrolidone (laurylpyrrolidone), ethanol, and a mixture of menthol and ethanol—on these parabens. The relationship between the permeability of these parabens and their octanol/water partition coefficients was also investigated, as well as the effects of the permeation enhancers on the fluidity of liposomes containing stratum corneum lipids. The results showed that in untreated guinea pig skin, the permeability of these parabens was positively correlated with their octanol/water partition coefficients. In lipid-depleted guinea pig skin, the permeability of parabens increased, and this was not correlated with their octanol/water partition coefficients. The effects of the permeation enhancers on paraben permeation varied. The osmosis enhancer increased the fluidity of the liposome lipid bilayer. Following intravenous infusion of ethylparaben in dogs, unhydrolyzed ethylparaben was found only in brain tissue. In the liver, kidneys, and muscle, it was immediately hydrolyzed to para-hydroxybenzoic acid. Six hours after oral administration of 1.0 g/kg ethylparaben to dogs, the peak plasma concentrations of free and total ethylparaben reached 427 and 648 μg/cm³, respectively. After 48 hours, all ethylparaben was completely cleared. Metabolism/Metabolites: Para-hydroxybenzoic acid is produced in pigs and Aspergillus. /Excerpt from Table/ Para-hydroxybenzoic acid esters are well absorbed in dogs, with ester bond hydrolysis and metabolic conjugation being the main clearance pathways. Similar metabolic patterns have been observed in humans. Parabens
Orally administered 14C-labeled ethyl paraben contains two major metabolites in the urine of cats: p-hydroxyhippuric acid and free p-hydroxybenzoic acid.
In mice, rats, rabbits, pigs, or dogs, ethyl paraben is excreted in urine as unmodified benzoate, p-hydroxybenzoic acid, p-hydroxyhippuric acid (p-hydroxybenzoylglycine), ester glucuronide, ether glucuronide, or ether sulfate.
For more complete metabolite/metabolite data on ethyl paraben (7 metabolites in total), please visit the HSDB record page.
Known human metabolites of ethyl paraben include (2S,3S,4S,5R)-6-(4-ethoxycarbonylphenoxy)-3,4,5-trihydroxyoxacyclohexane-2-carboxylic acid.
The pharmacokinetic properties of catalase are challenging due to its large molecular weight (~250 kDa) and poor cellular permeability. When administered intravenously, catalase has a short half-life in circulation, as it is rapidly cleared by the reticuloendothelial system. To overcome these limitations, catalase is often encapsulated in nanoparticles or conjugated to PEG to prolong its circulation time and enhance its tissue distribution. The volume of distribution is typically low, and the enzyme does not readily cross the blood-brain barrier. Pharmacokinetic studies in animal models have shown that nanoparticle encapsulation significantly improves the half-life and bioavailability of catalase.

Toxicity Summary
Identification and Uses: Ethyl parabens form colorless small crystals or a white powder. Ethyl parabens inhibits the growth of fungi and bacteria and is used as a preservative in pharmaceuticals, adhesives, and various cosmetic preparations. Human Exposure and Toxicity: Ethyl parabens are irritating to human skin. One human study did not find any sensitizing effects. Parabens are a class of general substances and rarely cause sensitization when applied to intact human skin. Application to damaged skin is a more common cause of sensitization. Oral administration of a mixture of methylparaben, ethylparaben, and propylparaben has been shown to exacerbate pre-existing skin problems. Animal Studies: Ethyl parabens are irritating to the eyes of rabbits. In laboratory animals, acute oral toxicity of ethylparaben is low. Limited long-term studies in rats have shown that ethylparaben has low toxicity and no carcinogenic activity was found. Dietary addition of ethylparaben can lead to proliferation of forestomach cells in rats. Limited Ames bacterial assays did not reveal mutagenicity. Ethylparaben did increase chromosomal aberrations in Chinese hamster ovarian cells, but similar effects were not observed in rats treated with ethylparaben. Oral administration of ethylparaben to pregnant female rats resulted in fetal toxicity at doses reaching maternal toxicity levels. Ethylparaben was not teratogenic in rats. An in vitro study showed that ethylparaben at concentrations as low as 8 mg/mL caused loss of sperm motility; however, an in vivo study showed that adding 0.1% or 1.0% ethylparaben to the diet of mice did not produce sperm toxicity.

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Interactions
The biological metabolic pathway of ethylparaben when co-administered with salicylic acid differs from that previously reported when ethylparaben was used alone.
The excretion of the hydrolysis product of ethylparaben—unconjugated paraben—is increased, while the excretion of the glycine conjugates of paraben—para-hydroxyhippuric acid and its ester glucuronide—is decreased. Blood concentration patterns differ significantly from those observed with ethylparaben alone, particularly with delayed elimination of all metabolites. Pharmacokinetic analysis of blood concentration data also revealed the effect of salicylic acid on the biometabolism of ethylparaben.

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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 items in total), please visit the HSDB record page.
The toxicity of catalase is generally low due to its endogenous nature and high specificity for hydrogen peroxide. However, potential immunogenicity and allergic reactions have been reported, particularly with catalase from non-human sources. In preclinical toxicology studies, catalase has been shown to be well-tolerated at therapeutic doses, with no significant adverse effects observed. High doses may lead to the production of oxygen bubbles in the bloodstream, a rare but serious complication. Overall, catalase is considered safe for research applications and has a favorable safety profile for therapeutic development.

[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.

Ethyl paraben is an ethyl ester formed by the condensation of the carboxyl group of 4-hydroxybenzoic acid with ethanol. It functions as an antibacterial food preservative, antifungal agent, plant metabolite, and phytoestrogen. It is both a preservative and an ethyl ester. Ethyl paraben is a standardized chemical allergen. Its physiological effects are achieved through increased histamine release and cell-mediated immunity. Ethyl paraben has been reported in Aeschynanthus bracteatus, Inula salsoloides, and other organisms with relevant data. Ethyl paraben is present in alcoholic beverages. It is an antibacterial and preservative. It is found in red wine, white wine, and sake. Ethyl paraben belongs to the hydroxybenzoic acid derivative family. These compounds contain hydroxybenzoic acid (or its derivatives), which refers to a benzene ring with a carboxylic acid group. Ethyl 4-hydroxybenzoic acid is a metabolite found or produced in Saccharomyces cerevisiae.
Catalase is a key enzyme in the antioxidant defense system, playing a crucial role in protecting cells from oxidative damage. Its expression and activity are altered in various pathological conditions, including cancer, aging, and neurodegenerative diseases. Due to its protective functions, catalase is being investigated for its potential in therapies against oxidative stress-related diseases. Recent clinical trials are exploring catalase mimetics and combination antioxidant therapies for neurodegenerative disorders. The enzyme is also used industrially in food preservation and in contact lens cleaning solutions.

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.)