PRODUCTS

ETHYLHEXYL STEARATE

2-ETHYLHEXYL STEARATE

CAS No.: 22047-49-0

Ethylhexyl stearate, also known as 2-Ethylhexyl Octadecanoate or Octyl stearate, is a palm derivative that is renewable in nature and widely used in the personal care industry. Stearate esters are prepared by the reaction between stearic acid and alcohol such as isopropyl, ethylhexyl, myistyl alcohol, cetyl, butyl, among others. Stearic acid can be obtained from animal sources as well as from vegetable oils. Ethylhexyl stearate is prepared by the reaction between stearic acid and ethylhexyl alcohol. Ethylhexyl stearate is a clear ester liquid that contains no suspended substances and is available in colorless liquid form. Since ethylhexyl alcohol forms a hydrophobic film when applied to the skin or lips, it has a unique low viscosity and oily texture. Thus, it softens the skin and gives a smooth appearance.

Synonyms:

ETHYLHEXYL STEARATE ; Octadecanoic acid ; 91031-48-0; 2-Ethylhexyl stearate ; 2-ETHYLHEXYL STEARATE; Stearic acid, octyl ester; 2-ethylhexyloctadecanoate; stearicacid,2-ethylhexylester; Octadecanoicacid,2-ethylhexylester ; Ethylhexyl stearate; ethyl hexyl stearate; etilhekzil stearat; etil hekzil stearat; 22047-49-0; 2-Ethylhexyl octadecanoate; Ethylhexyl stearate; Octadecanoic acid, 2-ethylhexyl ester; AK113740; W-110539; DSSTox_CID_27178; DSSTox_RID_82175; DSSTox_GSID_47178; SCHEMBL153398; Stearic acid 2-ethylhexyl ester; CHEMBL3184927; DTXSID9047178; Tox21_302619; AKOS015901877; KS-00000N16; NCGC00256861-01; CAS-22047-49-0; FT-0756635; NS00049187; Z4427; EC 244-754-0; M-8262; C-21648; Q27277167; 2-Ethylhexyl stearate, mixture of stearate and palmitate

Ethylhexyl stearate or octyl stearate is an ester of stearic acid with octanol. It is again one member of the groups called stearate esters which are obtained by reacting stearic acid with an alkyl group containing alcohol. Stearate esters all have unique properties of oily nature, but low viscosity and lighter feel. That’s why they are the choice of solvents in makeup related products. Stearic acid is obtained from various animal and plant source. It comes as clear to slightly yellowish liquid.

Stearic acid is also linked to skin’s natural fatty acid content, so it is ideal for skin preparation. Moreover, it imparts the right amount of viscosity to the product, it acts as a thickening agent as well. It also forms a film over the skin, a hydrophobic barrier which does not let the moisture pass through and escape from the skin. And without any greasy feel, it moisturizes the skin. It also nourishes the skin and provides a protective barrier; moist skin is healthy enough to fight any external inflammation. After regular application, resultant skin may become softer and smoother. It is most frequently used in skincare products, lipstick, skin makeup, and eye makeup.

Stearate esters act primarily as lubricants on the skin's surface, which gives the skin a soft and smooth appearance. Butyl Stearate also decreases the thickness of lipsticks, thereby lessening the drag on lips, and imparts water repelling characteristics to nail polishes. Butyl Stearate and Isopropyl Stearate dry to form a thin coating on the skin. Isocetyl Stearate can also be used to dissolve other substances, usually liquids.

The Food and Drug Administration (FDA) includes Butyl Stearate on its list as a flavoring agent allowed to be directly added to food. Butyl Stearate is also as an approvedindirect food additive and can be used as a component of adhesives. The safety of the stearate ester ingredients has been assessed by the Cosmetic ingredient (CIR) Expert Panel. The CIR Expert Panel evaluated scientific data and concluded that Butyl, Cetyl, Isobutyl, Isocetyl, Isopropyl, Myristyl and Ethylhexyl Stearate were safe as cosmetic ingredients. In 2003, as part of the scheduled re-evaluation of ingredients, the CIR Expert Panel considered available new data on the stearate esters and reaffirmed the above conclusion.

CIR Safety Review: The CIR Expert Panel noted that the safety of the stearate esters has been assessed in a number of studies. They had low acute oral toxicity and were essentially nonirritating to the eyes when tested at and above use concentrations. At cosmetic use concentrations, the stearate esters were, at most, minimally irritating to skin. In clinical studies, the stearate esters and cosmetics and personal care products containing them, were at most minimally to mildly irritating, essentially nonsensitizing, nonphototoxic and nonphotosensitizing.

The CIR Expert Panel indicated that comedogenicity should be considered when using the stearate ester ingredients in cosmetic formulations.

The stearate esters (Butyl Stearate, Cetyl Stearate, Isocetyl Stearate, Isopropyl Stearate, Myristyl Stearate, Ethylhexyl Stearate, Isobutyl Stearate) are oily liquids or waxy solids. Ethylhexyl Stearate may also be called Octyl Stearate. In cosmetics and personal care products, stearate esters are used most frequently in the formulation of eye makeup, skin makeup, lipstick and skin care products.

With increasing consumer concerns about personal health, the demand for personal care services and products is witnessing significant growth. Thus, it increases the market growth of ethylhexyl stearate as it is widely used as an ester in personal care products. Ethylhexyl stearate is often used as an emollient to prevent dehydration. For this reason, it is widely used as a solvent in emulsions, bath oils and cosmetic products. It is widely used in the production of formulations for skin makeup, lipsticks, eyeliner and other skin care products. Besides the personal care industry, ethylhexyl stearate is also widely used as an intermediate, lubricant, and surfactant. Because of these properties, ethylhexyl stearate is widely used in the production of metalworking fluids. It also offers good thermal stability and therefore finds application in aluminum rolling, also used in the production of ink additives and dyes. Therefore, the wide range of applications provides an opportunistic platform for the solid growth of the ethylhexyl stearate market over time.

However, with the increasing demand for organic and natural personal care products, various natural-based ingredients are used in the production of personal care products. Thus, it limits the market growth of ethylhexyl stearate. Moreover, stearic acid is derived from animal fat, further hindering the growth of the ethylhexyl stearate market with the increasing adoption of vegan-based products. Moreover, it causes mild eye irritation and produces a mild odor that may affect the adoption of ethyl stearate-based products among consumers.

The stearate esters are esters of stearic acid and an alcohol. Due to the grade of stearic acid and the alcohols used as starting materials, the commercially available stearate esters are often mixtures of various esters. The name indicates the ester at the highest concentration. In cosmetics and personal care products, the stearate esters function mainly as skin conditioning agents - emollients. Butyl Stearate also functions in lipsticks as a viscosity decreasing agent and a color-suspending agent. In nail polishes, Butyl Stearate may be used as a water-repelling plasticizer. In hand creams and lotions, Butyl and Isopropyl Stearate function as spreading agents. Isopropyl Stearate also serves to increase the gelatin characteristics of hand product formulations. Isocetyl Stearate is used in cosmetics and personal care products as a lubricant and solvent.

Ethylhexyl Stearate is used as an oil component for emulsions, bath oils, and as a solvent for active substances in cosmetics. Stearate esters are used most frequently in the formulation of eye makeup, skin makeup, lipstick and skin care products.

An emollient derived from plant oil that prevents water loss
Also known as Octyl Stearate
Ethylhexyl Stearate is used as an oil component for emulsions, bath oils, and as a solvent for active substances in cosmetics. Stearate esters are used most frequently in the formulation of eye makeup, skin makeup, lipstick and skin care products.

The CIR Expert Panel notes that the safety of the stearate esters has been assessed in a number of studies. They have low acute oral toxicity and are essentially non-irritating to the eyes. At cosmetic use concentrations, the stearate esters were, at most, minimally irritating to skin.

The substance 2-Ethylhexyl stearate is an ester of 2-ethylhexanol and stearic acid and meets the definition of a mono-constituent substance based on the analytical characterization.

2-Ethylhexyl stearate is liquid at room temperature and has a molecular weight of 396.69 g/mol and a water solubility < 0.05 mg/L at 25 °C (Frischmann, 2012). The log Pow is calculated to be 11.59 and the vapour pressure is estimated to be 0.000000139 Pa at 20 °C

Absorption is a function of the potential for a substance to diffuse across biological membranes. The most useful parameters providing information on this potential are the molecular weight, the octanol/water partition coefficient (log Pow) value and the water solubility. The log Pow value provides information on the relative solubility of the substance in water and lipids

The smaller the molecule, the more easily it will be taken up. In general, molecular weights below 500 are favourable for oral absorption . As the molecular weight of 2-Ethylhexyl stearate is 396.69 g/mol, absorption of the molecule in the gastrointestinal tract is in general anticipated.

Absorption after oral administration is also expected when the “Lipinski Rule of Five” (Lipinski et al. , refined by Ghose et al. (1999)) is applied to the substance 2-Ethylhexyl stearate, as all rules are fulfilled except for the log Pow, which is above the given range -0.4 to 5.6.

The log Pow of 11.59 suggests that 2-Ethylhexyl stearate is favourable for absorption by micellar solubilisation, as this mechanism is of importance for highly lipophilic substances (log Pow > 4), which are poorly soluble in water (1 mg/L or less).

After oral ingestion, esters of short-chain (C2-8) alcohols and fatty acids undergo stepwise chemical changes in the gastro-intestinal fluids as a result of enzymatic hydrolysis. The respective alcohol as well as the fatty acid is formed, even though it was shown in-vitro that the hydrolysis rate of methyl oleate was lower when compared with the hydrolysis rate of the triglyceride Glycerol trioleate (Mattson and Volpenhein, 1972). The physico-chemical characteristics of the cleavage products (e.g. physical form, water solubility, molecular weight, log Pow, vapour pressure, etc.) are likely to be different from those of the parent substance before absorption into the blood takes place, and hence the predictions based upon the physico-chemical characteristics of the parent substance do no longer apply (ECHA, 2008). However, also for both cleavage products, it is anticipated that they are absorbed in the gastro-intestinal tract. The highly lipophilic fatty acid is absorbed by micellar solubilisation (Ramirez et al., 2001), whereas the alcohol is readily dissolved into the gastrointestinal fluids and absorbed from the gastrointestinal tract.

Exemplarily, experimental data of the structurally similar Ethyl oleate (CAS No. 111-62-6) confirmed this assumption: The absorption, distribution, and excretion of 14C-labelled Ethyl oleate was studied in Sprague Dawley rats after a single, oral dose of 1.7 or 3.4 g/kg bw. It was shown that the test material was well (approximately 70–90%) absorbed

Overall, a systemic bioavailability of 2-Ethylhexyl stearate and/or the respective cleavage products in humans is considered likely after oral uptake of the substance.

The smaller the molecule, the more easily it may be taken up. In general, a molecular weight below 100 favours dermal absorption, above 500 the molecule may be too large (ECHA, 2008). As the molecular weight of 2-Ethylhexyl stearate is 396.69 g/mol, dermal absorption of the molecule cannot be excluded.

If the substance is a skin irritant or corrosive, damage to the skin surface may enhance penetration . As 2-Ethylhexyl stearate is not skin irritating in humans, enhanced penetration of the substance due to local skin damage can be excluded.

Based on a QSAR calculated dermal absorption a value < 0.00001 mg/cm²/event (very low) was predicted for 2-Ethylhexyl stearate (Danish EPA, 2010). Based on this value the substance has a low potential for dermal absorption.

For substances with a log Pow above 4, the rate of dermal penetration is limited by the rate of transfer between the stratum corneum and the epidermis, but uptake into the stratum corneum will be high. For substances with a log Pow above 6, the rate of transfer between the stratum corneum and the epidermis will be slow and will limit absorption across the skin, and the uptake into the stratum corneum itself is also slow. The substance must be sufficiently soluble in water to partition from the stratum corneum into the epidermis (ECHA, 2008). As the water solubility of 2-Ethylhexyl stearate is less than 1 mg/L, dermal uptake is likely to be (very) low.

Overall, the calculated low dermal absorption potential, the low water solubility, the molecular weight (>100), the high log Pow value and the fact that the substance is not irritating to skin implies that dermal uptake of 2-Ethylhexyl stearate in humans is considered as very limited.

2-Ethylhexyl stearate has a low vapour pressure of 0.000000139 Pa at 20 °C thus being of very low volatility. Therefore, under normal use and handling conditions, inhalation exposure and thus availability for respiratory absorption of the substance in the form of vapours, gases, or mists is not significant.

However, the substance may be available for respiratory absorption in the lung after inhalation of aerosols, if the substance is sprayed. In humans, particles with aerodynamic diameters below 100μm have the potential to be inhaled. Particles with aerodynamic diameters below 50μm may reach the thoracic region and those below 15μm the alveolar region of the respiratory tract (ECHA, 2008). Lipophilic compounds with a log Pow > 4, that are poorly soluble in water (1 mg/L or less) like 2-Ethylhexyl stearate can be taken up by micellar solubilisation.

Overall, a systemic bioavailability of 2-Ethylhexyl stearate esters in humans is considered likely after inhalation of aerosols with aerodynamic diameters below 15μm.

Highly lipophilic substances tend in general to concentrate in adipose tissue, and depending on the conditions of exposure may accumulate. Although there is no direct correlation between the lipophilicity of a substance and its biological half-life, it is generally the case that substances with high log Pow values have long biological half-lives. The high log Pow of > 5 implies that 2-Ethylhexyl stearate may have the potential to accumulate in adipose tissue .

However, as further described in the section metabolism below, esters of alcohols and fatty acids undergo esterase-catalysed hydrolysis, leading to the cleavage products 2-ethylhexanol and stearic acid.

The first cleavage product, 2-ethylhexanol, is moderately soluble in water (HSDB). The second cleavage product, the stearic acid, can be stored as triglycerides in adipose tissue depots or be incorporated into cell membranes. At the same time, stearic acid is also required as a source of energy. Thus, stored fatty acids underlie a continuous turnover as they are permanently metabolized and excreted. Bioaccumulation of fatty acids only takes place, if their intake exceeds the caloric requirements of the organism.

Overall, the available information indicates that no significant bioaccumulation in adipose tissue is anticipated.

Distribution within the body through the circulatory system depends on the molecular weight, the lipophilic character and water solubility of a substance. In general, the smaller the molecule, the wider is the distribution. If the molecule is lipophilic, it is likely to distribute into cells and the intracellular concentration may be higher than extracellular concentration particularly in fatty tissues.

2-Ethylhexyl stearate undergoes chemical changes as a result of enzymatic hydrolysis, leading to the cleavage products 2-ethylhexanol and stearic acid.

2-ethylhexanol, a rather small (MW = 130.22 g/mol) substance of moderate water solubility, will be distributed in aqueous compartments of the organism and may also be taken up by different tissues. Stearic acid is also distributed in the organism and can be taken up by different tissues. They can be stored as triglycerides in adipose tissue depots or they can be incorporated into cell membranes.

Overall, the available information indicates that the cleavage products, 2-ethylhexanol and stearic acid will be distributed in the organism.

Esters of fatty acids are hydrolysed to the corresponding alcohol (2-ethylhexanol) and fatty acid by esterases (Fukami and Yokoi, 2012). Depending on the route of exposure, esterase-catalysed hydrolysis takes place at different places in the organism: After oral ingestion, esters of alcohols and fatty acids undergo enzymatic hydrolysis already in the gastro-intestinal fluids. In contrast, substances that are absorbed through the pulmonary alveolar membrane or through the skin enter the systemic circulation directly before entering the liver where hydrolysis will basically take place.

The first cleavage product, 2-ethylhexanol, is mainly oxidized to 2-ethylhexanoic acid which is either glucuronidated or to a small extend further oxidized leading to various products.

The cleavage cleavage product, stearic acid, is stepwise degraded byβ-oxidation based on enzymatic removal of C2 units in the matrix of the mitochondria in most vertebrate tissues. The C2 units are cleaved as acyl-CoA, the entry molecule for the citric acid cycle. The omega- and alpha-oxidation, alternative pathways for oxidation, can be found in the liver and the brain, respectively.