Propane-1,2,3-triyl 3,5,5-trimethylhexanoate

Endpoint summary

Description of key information

Oral LD50 = 1253 mg/kg bw (worst-case assumption based on read-across from 3,5,5-trimethylhexanoic acid [CAS 3302-10-1] and after correction for differences in molecular weight and stoichiometry of full enzymatic hydrolysis)

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

02 - 18 June 1986

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 401 (Acute Oral Toxicity)

Deviations:

yes

Remarks:

no constant volume at the different dose levels, partially shorter acclimatisation period than 5 days

GLP compliance:

not specified

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

other: Bor:WISW (SPF TNO)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: F. Winkelmann, Borchen, Germany
- Weight at study initiation: 169.2 g (mean value)
- Fasting period before study: 16 h
- Housing: 1-5 animals per cage
- Diet: R10 Alleindiät für Ratten (Ssniff Spezialfutter, Soest, Germany), ad libitum
- Water: ad libitum
- Acclimation period: 4-8 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 ± 1
- Humidity (%): 60 ± 5
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12 / 12

Route of administration:

oral: gavage

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

MAXIMUM DOSE VOLUME APPLIED: 1.754 mL/kg bw

Doses:

631, 794, 1000, 1250 and 1580 mg/kg bw

No. of animals per sex per dose:

5

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: Animals were observed for mortality and clinical signs up to 6 h post-dose and daily thereafter. Animals were weighed prior to treatment and 1, 7 and 14 days after treatment.
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs, body weight, gross necropsy

Statistics:

Group mean body weights were calculated. The LD50 value and 95% confidence interval were calculated according to Litchfield and Wilcoxon (J Pharmacol Exp Ther 96:99, 1949).

Key result

Sex:

male/female

Dose descriptor:

LD50

Effect level:

1 160 mg/kg bw

Based on:

test mat.

Mortality:

631 and 794 mg/kg bw: No mortality occurred.
1000 mg/kg bw: 1/5 males and 2/5 females died within 24 h post-administration.
1250 mg/kg bw: 1/5 males and 5/5 females died within 24 h post-administration.
1580 mg/kg bw: 5/5 males and 5/5 females died within 31 h post-administration.

Clinical signs:

other: All animals showed clinical signs of toxicity. 15-30 min after dosage, animals showed ruffled fur, cowering, stagger, slight sedation and ataxia as well as prone position. Subsequently animals showed lacrimation, hypoactivity, diarrhoea, laboured breathin

Gross pathology:

Post mortem macroscopic examinations showed hyperaemia of stomach and intestinal mucosa, scattered discolouration of liver and kidneys and extensively filled urinary bladders. Further observations included hyperaemia of the mucosa of the urinary bladder in 1 animal, hyperaemia of the lung in 2 animals, hyperaemia of the pancreas in 4 animals, hyperaemia of the subcutis in 4 animals. Necroscopy of surviving animals at the end of the study revealed partially severe hyperaemia of the small intestinal mucosa.

Interpretation of results:

other: Acute tox. oral 4, H302. Classification according to Regulation (EC) No. 1272/2008 (CLP/EU GHS).

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

1 253 mg/kg bw

Quality of whole database:

The available information comprises an adequate, reliable (Klimisch score 2) and consistent study from a source substance (hydrolysis product). Read-across is justified based on the metabolism of propane-1,2,3-triyl 3,5,5-trimethylhexanoate, in particular on the fact that the substance undergoes enzymatic hydrolysis resulting in the formation of 3,5,5-trimethylhexanoic acid and glycerol. (refer to endpoint discussion for further details). The key study is supported by several studies with additional source substances. Therefore, the available information as a whole is sufficient to fulfil the standard information requirements set out in Annex VII, Item 8.5, in accordance with Annex XI, Item 1.5, of Regulation (EC) No. 1907/2006.

Acute toxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Acute toxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Justification for grouping of substances and read-across

There are no data available on the acute toxicity of propane-1,2,3-triyl 3,5,5-trimethylhexanoate (CAS 56554-53-1). In order to fulfil the standard information requirements set out in Annex VII, Item 8.5, in accordance with Annex XI, Item 1.5, of Regulation (EC) No. 1907/2006, read-across from a structurally related substance and common hydrolysis products is conducted. In accordance with Article 13(1) of Regulation (EC) No. 1907/2006, "information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI are met.” In particular for human toxicity, information shall be generated whenever possible by means other than vertebrate animal tests, which includes the use of information from structurally related substances and/or hydrolysis/biodegradation products (grouping or read-across).

Having regard to the general rules for grouping of substances and read-across approach laid down in Annex XI, Item 1.5, of Regulation (EC) No. 1907/2006, whereby physico-chemical, toxicological and ecotoxicological properties may be predicted from data for reference substance(s) by interpolation to other substances on the basis of structural similarity, glycerides, C8-18 and C18-unsatd. mono- and di-, acetates (CAS 91052-13-0) was selected as reference substances for assessment of the acute oral toxicity of propane-1,2,3-triyl 3,5,5-trimethylhexanoate. In addition, the hydrolysis products 3,5,5-trimethylhexanoic acid (CAS 3302-10-1) and glycerol (CAS 56-81-5) were chosen as reference substances. The read-across is based on the metabolism of propane-1,2,3-triyl 3,5,5-trimethylhexanoate, in particular on the fact that the substances undergoes enzymatic hydrolysis resulting in the formation of 3,5,5-trimethylhexanoic acid and glycerol. A detailed analogue approach justification is provided in the technical dossier (see IUCLID Section 13).

Overview of acute toxicity

CAS#	56554-53-1	3302-10-1	56-81-5	91052-13-0
Chemical name	Propane-1,2,3-triyl 3,5,5-trimethylhexanoate	3,5,5-Trimethylhexanoic acid	Glycerol	Glycerides, C8-18 and C18-unsatd. mono- and di-, acetates
Molecular weight	512.78	158.24	92.10	302.36 - 442.63
Acute toxicity oral	RA: CAS 3302-10-1 RA: CAS 56-81-5 RA: CAS 73398-61-5 RA: CAS 91052-13-0	Experimental result: LD50 (rat, m/f) = 1160 mg/kg bw	Experimental result: LD50 (rat, f) = 27260 mg/kg bw	Experimental result: LD50 (rat, f) >2000 mg/kg bw
Acute toxicity inhalation	Waiving	--	--	--
Acute toxicity dermal	Waiving	--	--	Experimental result: LD50 (rat, m/f) >2000 mg/kg bw

--: Data lacking

 Oral

CAS 3302-10-1

An acute oral toxicity study was conducted with 3,5,5-trimethylhexanoic acid according to OECD guideline 401 (Hüls, 1986). Groups of rats (5 per sex and dose) received single oral doses of the undiluted test material at 631, 794, 1000, 1250 and 1580 mg/kg bw. Animals were weighed weekly and observed daily for mortality and clinical signs up to the end of the 14-day observation period. No effects on body weight (gain) were observed. No mortality occurred in animals given 631 and 794 mg/kg bw. One male and 2 females of the 1000 mg/kg bw group and 1 male and 5 females of the 1250 mg/kg bw group died within 24 h post-administration. In the 1580 mg/kg bw group, all males and females died within 31 h post-dose. Starting 15-30 min and up to 48 h after treatment all animals showed clinical signs of toxicity, which included ruffled fur, cowering, stagger, (slight to severe) sedation, ataxia, prone position, lacrimation, hypoactivity, diarrhoea, laboured breathing, gasping respiratory sounds, hypothermia, trembling and wide opened eyes. Post mortem macroscopic examinations showed hyperaemia of stomach and intestinal mucosa, scattered discolouration of liver and kidneys and extensively filled urinary bladders. Further observations included hyperaemia of the mucosa of the urinary bladder in 1 animal, hyperaemia of the lung in 2 animals, hyperaemia of the pancreas in 4 animals, hyperaemia of the subcutis in 4 animals. Necroscopy of surviving animals at the end of the study revealed partially severe hyperaemia of the small intestinal mucosa. The LD50 value was calculated to be 1160 mg/kg bw (95% confidence interval: 1018-1322). Based on the study results, the substance is considered to be harmful if swallowed.

CAS 56-81-5

In early studies, Hine et al. (1953a,b,c) investigated the acute oral toxicity of natural and synthetic (99.5% pure) glycerol in female rats, male mice and male guinea pigs. Twelve rats were given a single oral dose of either natural or synthetic glycerol at 27260 mg/kg bw by gavage. Similarly, 91 mice received the test material(s) at 15000 to 31500 mg/kg bw. Three dose levels were administered to guinea pigs, from which only the middle dose (7250 mg/kg bw) was explicitly reported. All animals were observed for mortality, body weight changes and clinical signs of toxicity over a period of 10 days. Thereafter, gross necropsy and histopathological examinations were conducted on all dead animals and selected survivors.

Stimulation of the central nervous system was identified as the leading pharmacological effect. Mortality in rats was preceded by muscle spasms and clonic convulsions. Respiratory failure occurred 15-2.25 h post-dose. Within 2.5 h, survivors appeared normal. In mice, Clinical signs preceding death included body tremors, erection of the tail in typical Straub manner and generalised clonic convulsions. Immediately after dosing, clinical signs observed in guinea pigs were tremors of the head and body, initiated by auditory stimuli. Tremors usually preceded death, but not animals showing tremors died.

Organ lesions observed in rats included hyperaemia of the pylorus and small intestine, lung congestion, pale spleen. In 3/12 rats, hyperaemia of the cerebral meninges was noted. In some mice, hyperaemia of the small intestine and lungs was observed at the higher dose levels. The authors noted that the only other lesion of interest was slight hyperaemia of the kidneys and of the mucosa of the small intestine. For guinea pigs, lesions observed were reported to be similar to those seen in rats.

The oral LD50 of both natural and synthetic glycerol was 27260 and 23000 mg/kg bw in rats and mice, respectively. In guinea pigs, the LD50 values were 10000 and 11500 mg/kg bw for natural and synthetic glycerol, respectively. The results of the studies showing very high oral LD50 values in three species provide sufficient evidence that glycerol is not acutely toxic by the oral route.

CAS 91052-13-0

In a GLP-compliant gavage study investigating the acute oral toxicity of Glycerides, C8-18 and C18-unsatd. mono- and di-, acetates, female Sprague Dawley were exposed to a limit dose of 2000 mg/kg bw in a stepwise procedure (3 rats per step) according to OECD guideline 423 (Notox, 2010a). No mortality was observed up to the end of the14-day observation period. Clinical signs involved hunched posture and/or piloerection in all females on Day 1 of the observation period. All animals showed the expected gain in body weights during the study and necropsy revealed no substance-related findings. Based on the results, the oral LD50 value for female Sprague Dawley rats is > 2000 mg/kg bw. In accordance with OECD guideline 423, the oral LD50 cut-off of the test substance is considered to > 5000 mg/kg bw.

For the purpose of hazard assessment of propane-1,2,3-triyl 3,5,5-trimethylhexanoate, the lowest dose descriptor (LD50 = 1253 mg/kg bw) available from the reference substances is selected as starting point. The available in vitro data on enzymatic ester hydrolysis of propane-1,2,3-triyl 3,5,5-trimethylhexanoate suggest that about 30% of the substance will be fully hydrolysed to 3,5,5-trimethylhexanoic acid and glycerol within 4 h in the gastrointestinal tract, from which they can readily be absorbed (Oßberg, 2012). It cannot be ruled out, that the parent substance or a fraction of it may be absorbed unchanged and be hydrolysed within the body, e.g. in the liver. Therefore, in a worst case approach, 100% hydrolysis and bioavailability of 3,5,5-trimethylhexanoic acid is assumed. In order to correct the dose descriptor for differences in molar mass, it is thus assumed that hydrolysis of 1 mole propane-1,2,3-triyl 3,5,5-trimethylhexanoate (512.78 g) results in the formation of 3 mole 3,5,5-trimethylhexanoic acid (3 x 158.24 g = 474.72 g). Hence, the oral LD50 of propane-1,2,3-triyl 3,5,5-trimethylhexanoate is estimated to be 1253 mg/kg bw (= 1160 mg/kg bw x [512.78/474.72]), and the substance is therefore considered as harmful if swallowed.

Inhalation

Inhalation is not a relevant route of exposure for propane-1,2,3-triyl 3,5,5-trimethylhexanoate. Exposure of humans via inhalation is unlikely given the low vapour pressure (< 0.0001 Pa at 20°C) of the substance and its use.

Dermal

The molecular weight and physico-chemical properties (water solubility < 0.05 mg/L; log Kow > 10) of propane-1,2,3-triyl 3,5,5-trimethylhexanoate are in a range which anticipates a low to very low dermal absorption. The substance is not skin irritating in vitro and in a Local Lymph Node Assay the substance was identified as a moderate skin sensitiser (EC3 value of 70%), but no mortality and no other signs of systemic toxicity were observed. The estimated oral LD50 is 1253 mg/kg bw (see above), which is based on the assumption of 100% ester hydrolysis by gastrointestinal enzymes. While the rate of enzymatic hydrolysis in the gastrointestinal tract is generally high, thereby fulfilling a normal physiological function, the rate of hydrolysis in the skin is anticipated to be comparatively low. The weight of evidence from the available physico-chemical and toxicological data thus indicates that propane-1,2,3-triyl 3,5,5-trimethylhexanoate is not considered to be acutely toxic by the dermal route.

Conclusions for acute toxicity

There are no data available on the acute toxicity of propane-1,2,3-triyl 3,5,5-trimethylhexanoate. Following oral exposure, the substance is anticipated to undergo enzymatic hydrolysis in the gastrointestinal tract prior to absorption and/or within the body, e.g. in the liver. Therefore, the available data on the hydrolysis products 3,5,5-trimethylhexanoic acid and glycerol are taken into account for assessment of the endpoint acute oral toxicity by means of read-across in a worst-case approach. The oral LD50 values of 3,5,5-trimethylhexanoic acid and glycerol in rats are 1160 and 27260 mg/kg bw, respectively. The oral LD50 of the analogue substance glycerides, C8-18 and C18-unsatd. mono- and di-, acetates > 2000 mg/kg bw. The lower dose descriptor was selected as starting point for hazard assessment. After correction for differences in molecular weight and considering the stoichiometry of ester hydrolysis, the LD50 value of propane-1,2,3-triyl 3,5,5-trimethylhexanoate is estimated to be 1253 mg/kg bw. The substance is therefore considered to be harmful if swallowed.

Human exposure by inhalation is unlikely given the low vapour pressure and uses of propane-1,2,3-triyl 3,5,5-trimethylhexanoate.

Based on the weight of evidence from the physico-chemical (high molecular weight, low water solubility, high log Kow) and relevant toxicological studies (skin irritation and skin sensitisation) along with the available data on the acute oral toxicity of the hydrolysis products, the dermal absorption of propane-1,2,3-triyl 3,5,5-trimethylhexanoate is anticipated to be low to very low and the substance is considered to be not acutely toxic after dermal exposure.

Justification for classification or non-classification

Based on read-across following an analogue approach, the available data on acute oral toxicity of propane-1,2,3-triyl 3,5,5-trimethylhexanoate meet the classification criteria for Acute toxicity Category 4 (H302: Harmful if swallowed) according to Regulation (EC) No. 1272/2008. There are no data available on acute toxicity by the inhalation and dermal routes.