1-ethynylcyclohexyl acetate

Endpoint summary

Description of key information

Acute oral toxicity: Based on read across information from Ambrate (similar to OECD TG 401):LD50 = 680 mg/kg bw.

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Reference 1

Endpoint:

acute toxicity: oral

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

2017

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Results derived from a valid read across, with adequate and reliable documentation / justification.

Justification for type of information:

The read across justification is presented in the Acute Toxicity Endpoint summary. The corresponding documentation file is also attached there.

Reason / purpose for cross-reference:

read-across source

Key result

Sex:

not specified

Dose descriptor:

LD50

Effect level:

680 mg/kg bw

Based on:

other: read across information

95% CL:

>= 440 - <= 1 050

Interpretation of results:

other: Acute oral toxicity Category 4

Remarks:

According to EU CLP Regulation (EC) No. 1272/2008 and its amendments.

Conclusions:

The acute oral LD50 for Herbacet #1 is considered to be 680 mg/kg bw, based on read across information from Ambrate.

Reference 2

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Not reported.

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

pre-GLP study, limited documented

Justification for type of information:

Information used for read across to Herbacet #1.

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 401 (Acute Oral Toxicity)

GLP compliance:

no

Remarks:

pre-GLP

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

not specified

Sex:

not specified

Details on test animals or test system and environmental conditions:

TEST ANIMALS
No details.
ENVIRONMENTAL CONDITIONS
No details.

Route of administration:

oral: unspecified

Vehicle:

not specified

Details on oral exposure:

No details.

Doses:

300, 600, 1220, and 5000 mg/kg bw

No. of animals per sex per dose:

10 animals per dose

Control animals:

no

Details on study design:

- Duration of observation period following administration: 11 days
- Frequency of observations and weighing: No data
- Necropsy performed: yes
- Other examinations performed: clinical signs

Key result

Sex:

not specified

Dose descriptor:

LD50

Effect level:

680 mg/kg bw

Based on:

test mat.

95% CL:

>= 440 - <= 1 050

Mortality:

300 mg/kg bw: 2/10 died; deaths were observed on day 1 and day 3.
600 mg/kg bw: 4/10 died; deaths were observed on day 1 (3 animals) and on day 11 (1 animal).
1220 mg/kg bw: 8/10 died; deaths were observed on day 1 (4 animals), day 2 (3 animals) and on day 10 (1 animal).
5000 mg/kg bw: 10/10 died; deaths were observed on day 1 (7 animals) and on day 2 (3 animals).

Clinical signs:

other: 300 mg/kg bw: no clinical signs were observed. 600 mg/kg bw: lethargy, ptosis and piloerection. 1220 mg/kg bw: flaccid tone. 5000 mg/kg bw: lethargy, ataxia and coma.

Gross pathology:

Necropsy observations:
300 mg/kg bw: Intestines, red areas (1/10); intestines, yellow areas (2/10); liver, mottled (2/10); lungs, dark areas (4/10); kidneys dark (2/10)
600 mg/kg bw: Exudate, nose/mouth (1/10); intestines, yellow areas (3/10); intestines, bloated (1/10), liver dark (2/10); liver, mottled (3/10); lungs dark (1/10); lungs, dark areas (3/10); kidneys dark (3/10); kidneys, mottled (3/10); spleen large (1/10).
1220 mg/kg bw: Exudate, nose/mouth (1/10); exudate, anogenital (2/10), intestines, red areas (1/10); intestines, yellow areas (5/10); liver dark (2/10); liver, mottled (4/10); lungs dark (1/10); lungs, dark areas (4/10); kidneys dark (6/10); kidneys, mottled (2/10); spleen large (2/10).
5000 mg/kg bw: Exudate, nose/mouth (10/10); exudate, anogenital (3/10); intestines, red areas (1/10); intestines, yellow areas (10/10); intestines, bloated (7/10), liver, mottled (10/10); lungs dark (10/10); kidneys dark (10/10); blood in bladder (3/10).

Interpretation of results:

other: Acute oral toxicity Category 4

Remarks:

According to EU CLP Regulation (EC) No. 1272/2008 and its amendments.

Conclusions:

The acute oral LD50 in rats was determined to be 680 mg/kg bw.

Executive summary:

In an acute oral toxicity study, performed similar to OECD TG 401 (pre-OECD, pre-GLP, rated Klimisch 2), 4 groups of 10 rats were orally exposed to the test substance and observed for signs of toxicity for a period of 11 days. At 300, 600, 1220 and 5000 mg/kg bw, respectively 2/10, 4/10, 8/10 and 10/10 animals died. Deaths occurred on day 1, 2, 3, 10 and 11. Clinical signs observed were lethargy, ptosis, piloerection, flaccid tone, ataxia and coma. At necropsy following effects were observed: exudate from nose/mouth and anogenital exudate, in the intestines red and yellow areas were observed and bloated intestines, dark livers and mottled livers, dark lungs and dark areas in the lungs, dark kidneys and mottled kidneys, large spleens, and blood in the bladder. Based on the results, a LD50 of 680 mg/kg bw was obtained in the acute oral toxicity study with rats.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

680 mg/kg bw

Quality of whole database:

The acute oral toxicity result is of sufficient quality and adequate for this dossier.

Additional information

First the experimental information of Ambrate is presented being used for read across to Herbacet #1 and thereafter the read across justification.

Ambrate acute oral toxicity:

In an acute oral toxicity study, performed similar to OECD TG 401 (pre-OECD, pre-GLP, rated Klimisch 2), 4 groups of 10 rats were orally exposed to the test substance and observed for signs of toxicity for a period of 11 days. At 300, 600, 1220 and 5000 mg/kg bw, respectively 2/10, 4/10, 8/10 and 10/10 animals died. Deaths occurred on day 1, 2, 3, 10 and 11. Clinical signs observed were lethargy, ptosis, piloerection, flaccid tone, ataxia and coma. At necropsy following effects were observed: exudate from nose/mouth and anogenital exudate, in the intestines red and yellow areas were observed and bloated intestines, dark livers and mottled livers, dark lungs and dark areas in the lungs, dark kidneys and mottled kidneys, large spleens, and blood in the bladder. Based on the results, a LD50 of 680 mg/kg bw was obtained in the acute oral toxicity study with rats.

Read across justification:

The acute oral toxicity of Herbacet#1 (CAS 5240-32-4) using read across from Ambrate (CAS 37172-05-7)

 

Introduction and hypothesis for the analogue approach

Herbacet#1 is a cyclohexane with an ethynyl and acetate group attached to the same carbon atom. For this substance no acute oral toxicity data are available.

In accordance with Article 13 of REACH, lacking information should be generated whenever possible by means other than vertebrate animal tests, i.e. applying alternative methods such as in vitro tests, QSARs, grouping and read-across. For assessing the acute oral toxicity of Herbacet#1 the analogue approach is selected because for one closely related analogue acute oral toxicity information is available which can be used for read across.

Hypothesis: Herbacet#1 has similar acute oral toxicity compared to Ambrate resulting in a similar LD50.

Available information: The source chemical Ambrate (Cas no. 37172-05-7) has been tested in an acute oral toxicity test up to 5000 mg/kg bw, similar to OECDTG 401, with an 11-day observation period, resulting in a LD50 of 680 mg/kg bw. The test result receives a reliability of 2 (pre-GLP).

Target chemical and source chemical(s)

Chemical structures of Herbacet#1 and Ambrate are shown in the data matrix, including physico-chemical properties and toxicological information, thought relevant for acute oral toxicity, of both substances.

Purity / Impurities

Herbacet#1 is a mono-constituent. The purity and impurities do not indicate acute oral toxicity potential other than indicated by the parent substance. The impurities are all below < 10%.

Analogue approach justification

According to Annex XI 1.5 read across can be used to replace testing when the similarity can be based on a common backbone and a common functional group. When using read across the result derived should be applicable for C&L and/or risk assessment and it should be presented with adequate and reliable documentation.

Analogue selection:In order to identify possible RA candidates, the RIFM database and OECD QSAR toolbox were used for a search of analogues.From the RIFM database two analogues were found of which only Ambrate has an ethynyl group.In the OECD QSAR toolbox, using Tanimoto with 60% threshold for similarity, 10 additional structures were found.From the identified analogues, Ambrate is most similar in structure to Herbacet#1 (Tanimoto 65%; ethynyl and acetate group) and has reliable acute oral toxicity data.

Structural similarities and differences:Herbacet#1 and Ambrate have a similar backbone and functional group, i.e. cyclohexane with an ethynyl group and an acetate ester on C1. The difference between both substances is that Ambrate has an additional sec-butyl group on C2. This group does not stericallcy hinder the ethynyl or the ester group as can be seen when looking into the 3-D structure of the molecule.

Toxico-kinetic:Absorption: Herbacet#1 andAmbrateindicate similar absorption based on the similarity in chemical structure and physico-chemical properties. Herbacet#1 and Ambrate have molecular weights and log Kows favorable for uptake via the oral route. The extra sec-butyl group in Ambrate results in a somewhat higher log Kow and lower water solubility than Herbacet#1, but both substances are in the same range for good oral absorption.Metabolism: The ester bond in Herbacet#1 and Ambratewill hydrolyse into the respective alcohol, 1-ethynylcyclohexanol and 2-sec-butyl-1-ethynylcyclohexanol respectively, and acetic acid due to activity of carboxylases in the gut and liver (Belsito et al., 2008, Wu et al., 2010). This hydrolysis is depicted in Figure 1.

Fig.1    Herbacet#1 and its analogues are presented together with the measured and anticipated acute oral rat LD50s.

In addition, according to De Vito (2012) theethynyl groupcan also metabolise via an oxirene intermediate into a ketene metabolite: R-C=C=O.

Toxico-dynamics:The reactive site of Herbacet#1 and Ambrate is the ethynyl group which is similar in both substances.The ketene groupformed after the metabolisation of the ethynyl group is highly electrophilic, andthus reactive, possiblycausing the toxicity (De Vito, 2012).

Uncertainty of the prediction:The derived LD50 for Herbacet#1 is supported with LD50 information from 1-ethynylcyclohexanol (Cas no. 78-27-3, ECHA dissemination site), the hydrolysis product of Herbacet#1, which has an LD50 of 600 mg/kg bw (test is similar to OECD TG 401). There is also other LD50 information from Ambrate: 364 mg/kg bw. This LD50 is in the same toxicity range as the 680 mg/kg bw LD50 of the selected study. This latter LD50 is more similar to the 600 mg/kg bw from Herbacet’s hydrolysis product and therefore this 680 mg/kg bw is selected as key value. In view of Ambrate and 1-ethynylcyclohexanol having almost the same LD50 it can be assumed that the additional sec-butyl group in Ambrate, but not in Herbacet#1, is not affecting a difference in LD50. Based on this a conversion of the LD50 value is also not needed.

Data matrix

The relevant information on physico-chemical properties and toxicological characteristics are presented in the Data Matrix.

Conclusions per endpoint for Hazard Assessment

When using read across the result derived should be applicable for C&L and/or risk assessment and be presented with adequate and reliable documentation, as is shown above. For Ambrate a well conducted acute oral toxicity test is available (Reliability 2) with a LD50 of 680 mg/kg bw which can be used for read across to Herbacet#1. Based on these data for Herbacet#1 also a LD50 of about 680 mg/kg bw can be derived for the endpoint acute oral toxicity.

Final conclusion on Hazard:Herbacet#1 has an acute oral LD50 of 680 mg/kg bw.

 

References:

Belsito, D., Bickers, D., Bruze, M., Calow, P., Greim, H., Hanifin, J.M., Rogers, A.E., Saurat, J.H., Sipes, I.G., Tagami, H., 2008, A toxicologic and dermatologic assessment of cyclic acetates when used as fragrance ingredients, Food and Chemical Toxicology 46, Suppl 12:S1-27.

 

De Vito, S., 2012, Structural and toxic mechanism-based approaches to designing safer chemicals, Green Processes, Eds. Boethling, R. and Vouchkova, A., Volume 9, Chapter 4, 77-106 (page 82 and 83, specifically)

 

Wu, S., Blackburn, K., Amburgery, J., Jaworska, J., and Federle, T., 2010, A framework for using structural, reactivity, metabolic and physico-chemical similarity to evaluate the suitability of analogs for SAR-based toxicological assessments, Regul. Toxicol. Pharmacol., 56, 67-81.

 

Data matrix for the read across to Herbacet#1 from Ambrate.

Common names	Herbacet#1 (Target)	Ambrate (Source)
Chemical structures
CAS no	5240-32-4	37172-05-7
EC no	226-040-0	253-378-6
Reach registration	Annex VII
Empirical formula	C10H14O2	C14H22O2
Physico-chemical data
Molecular weight	166.22	222.33
Physical state	liquid	liquid
Melting point,^oC	<-20 (m) 31.14 (EPISUITE)	60.18 (EPISUITE)
Water solubility, mg/L	738.7 (m) 252.3 (EPISUITE)	3.70 (EPISUITE)
Log Kow	2.8 (m) 2.82 (EPISUITE)	4.63 (EPISUITE)
Human health endpoints
Acute oral tox (LD50), mg/kg bw	Read across	680

 

Justification for classification or non-classification

The substance needs to be classified for acute oral toxicity category 4 and labelled with H302: Harmful if swallowed according to EU CLP Regulation (EC) No. 1272/2008 and its amendments.