Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1)

Endpoint summary

Description of key information

Assessment of the Toxicokinetic Behaviour

Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) (CAS-No. 68527-63-9; EC-No. 271-272-8)

There are no studies available in which the toxicokinetic properties of Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) were investigated.

Therefore, in accordance with Annex VIII, Column 1, Item 8.8 of Regulation (EC) 1907/2006 and with Guidance on information requirements and chemical safety assessment Chapter R.7c: Endpoint specific guidance (ECHA, 2012), assessment of the toxicokinetic behaviour of the substance Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) was conducted based on the relevant available information.

This comprises a qualitative assessment of the available substance-specific data on physico-chemical and toxicological properties according to `Guidance on information requirements and chemical safety assessment Chapter R.7c: Endpoint specific guidance‘ (ECHA, 2012).

Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) (molecular weight 504.77 g/mol) is a red brownish liquid, which is good soluble in water (45 g/L; key study; see chapter 4.8 water solubility).

The calculated log Po/w is 1.14 for the compound Diethyl sulphate and 7.51 for the second compound 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (QSAR estimation KOWWIN v1.68, see chapter 4.7 partition coefficient), indicating lipophilie and that a general accumulation of Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) may be possible. The vapour pressure of 0,000082 Pa at 20 °C (key study, see chapter 4.6 vapour pressure) is very low.

Absorption

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 (ECHA, 2012).

Oral

The smaller the molecule, the more easily it will be taken up. In general, molecular weights below 500 g/mol are favourable for oral absorption (ECHA, 2012). As the molecular weight of Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) is approx. 505 g/mol absorption of these molecules in the gastrointestinal tract is not very likely. But the molecule contains several sites for metabolism (e.g. for hydrolysis, oxidation) and allows ring opening and degradation of the aliphatic chains. It is therefore considered that both metabolic conversion and metabolic breakdown will take place.

In the gastrointestinal tract (GIT), metabolism prior to absorption via enzymes of the microflora may occur. The physico-chemical characteristics of the cleavage products (e.g. physical form, water solubility, molecular weight, log Pow, vapour pressure, etc.) will 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, 2012). However, for the cleavage products, it is anticipated that they will be absorbed in the gastro-intestinal tract.

The available data on oral toxicity of Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) are considered for assessment of oral absorption.
In an acute oral toxicity study based on OECD Guideline 423, the LD50 cut-off value of the of test item Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) is 500 mg/kg body weight. All 3 animals were found dead 1 day after dosing of 2000 mg/kg bw.

No abnormality was found. Therefore, bioavailability of Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) after oral administration is indicated.

In a Combined repeated dose toxicity study with the reproduction/developmental toxicity screening test according to OECD 422 the test item was administered to wistar rats in the oral doses of 0, 13, 40 and 130 mg/kg bw daily. It can be concluded that the oral administration of test substance in male and female Wistar rats produced lesions of varied degrees in liver of both males and females. These lesions correlated only in G4 males with increased AST serum level and seem to be test item related in this dosage but cannot clearly interpreted as test item related in the lower dose groups of both sexes as several lesions were also found in the control groups. The lesions in testes and epididymis along with increased serum AST, calcium and phosphorous levels in males at 130 mg/kg body weight is considered test item related; whereas lesions in testes and epididymis along with increased serum calcium and phosphorous levels in males at 40 mg/kg body weight is considered to be test item related. However, no adverse pathological alterations were observed in the low dose group of male animals. In females no adverse pathological alterations can be interpreted as test item related except some more alterations in the liver in the highest dose group as compared to the control. Therefore, the NOAEL for general toxicity in males is considered to be 13 mg/kg bw whereas the NOAEL for general toxicity in females is considered to be 40 mg/kg bw under the test conditions (OECD422 key study; see chapter 7.5.1 repeated dose oral).

In summary, the above discussed physical-chemical properties of Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) and relevant data indicate absorption and metabolic conversion and metabolic breakdown before absorption. For risk assessment purposes the oral absorption of Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) is set at 100% as a worst-case assumption.

Dermal

The smaller the molecule, the more easily it may be taken up. In general, a molecular weight below 100 g/mol favours dermal absorption, above 500 g/mol the molecule may be too large (ECHA, 2012). As the molecular weight of of Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) is above 500 g/mol only a very small amount will be absorbed by skin.

If the substance is a skin irritant or corrosive, damage to the skin surface may enhance penetration (ECHA, 2012). In an acute dermal toxicity study a single dose level of 2000 mg/kg of Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) was administered to Wistar rats (key study, see chapter 7.2.3 acute dermal toxicity). No signs of systemic toxicity were observed, indicating primarily a low dermal toxicity (the LD50 value of the test item is more than 2000 mg/kg body weight). Well defined erythema and slight oedema were observed in all the animals. At 48 & 72 hours observation the animals showed slight to well defined erythema, two animals showed moderate to severe erythema. Moderate oedema was also observed in some animals. Therefore, penetration of the substance due to local skin damage cannot be excluded.

The potential of diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) to cause skin sensitisation was examined in a study according to OECD 442B. Based on this study, using 1%, 0.5% and 0.25% (v/v) of the test item skin sensitization was produced in mice.

Overall, due to the experimental low dermal toxicity, but the presence of skin irritation and skin sensitization, a dermal absorption of Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) of 50% is considered as worst case.

Inhalation

Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) has a very low vapour pressure of 0,000082 Pa at 20 °C (key study, see chapter 4.6 vapour pressure) thus being of 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 expected to be 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 100 μm have the potential to be inhaled. Particles with aerodynamic diameters below 50 μm may reach the thoracic region and those below 15 μm the alveolar region of the respiratory tract (ECHA, 2012).

Any lipophilic compound may be taken up by micellular solubilisation, but this mechanism may be of particular importance for highly lipophilic compounds (log P >4), particularly those that are poorly soluble in water (1 mg/l or less) that would otherwise be poorly absorbed.

Esterases present in the lung lining fluid may also hydrolyse the substance, hence making the resulting alcohol and acid available for respiratory absorption. Due to the high molecular weight of the substance, absorption is driven by enzymatic hydrolysis of the ester to the respective metabolites and subsequent absorption.

Therefore, respiratory absorption of Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) is considered to be possible.

Overall, a systemic bioavailability of Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) in humans is considered likely, too.

Distribution

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 (ECHA, 2012).

Furthermore, the concentration of a substance in blood or plasma and subsequently its distribution is dependent on the rate of absorption.

As discussed above absorption of Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) is indicated as the acute oral toxicity study and the combined repeated dose toxicity study with the reproduction/developmental toxicity screening test show.

Nevertheless, Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) will undergo chemical changes as a result of enzymatic hydrolysis, leading to several cleavage products which are metabolized and distributed in the organism.

Metabolism

The effects observed in the Combined repeated dose toxicity study with the reproduction/develop-mental toxicity screening test according to OECD 422 reveal a potential for toxicity after repeated exposure. Based on these data and on the properties of the test substance characteristics absorption of Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) is assumed.

Accumulation

Highly lipophilic substances in general tend 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. (ECHA, 2012).

However, as described, Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) contains several sites for metabolism (e.g. for hydrolysis, oxidation) and allows ring opening and degradation of the aliphatic chains. It is therefore considered that both metabolic conversion and metabolic breakdown counteract to the trend for bioaccumulation. In summary the substance is unlikely to bioaccumulate

Excretion

The potentional metabolic breakdown products due to hydrolysis and/or oxidation, ring opening and degradation of the aliphatic chain are assumed to may either further be metabolized or conjugated to polar products (e.g. glucuronides, sulfates, etc.) or excreted unchanged via urine. The conjugates will either be excreted via the bile (high (>500) molecular weight compounds) or the urine (low (<500) molecular weight compounds).

Key value for chemical safety assessment

Absorption rate - oral (%):

100

Absorption rate - dermal (%):

50

Absorption rate - inhalation (%):

100