Triisotridecyl benzene-1,2,4-tricarboxylate

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics

Type of information:

migrated information: read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study with acceptable restrictions. Limited details on environmental conditions. Some minor polar metabolites in the faeces could not be identified.

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1984

Report date:

1984

Reference 2

Reference Type:

secondary source

Title:

TRIS(2-ETHYLHEXYL)BENZENE-1,2,4-TRICARBOXYLATE CAS N°: 3319-31-1

Author:

OECD

Year:

2002

Bibliographic source:

UNEP publications

Materials and methods

Objective of study:

absorption

distribution

excretion

metabolism

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 417 (Toxicokinetics)

Deviations:

yes

Remarks:

Limited details on environmental conditions. Some minor polar metabolites in the faeces could not be identified.

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Tris(2-ethylhexyl) benzene-1,2,4-tricarboxylate

EC Number:

222-020-0

EC Name:

Tris(2-ethylhexyl) benzene-1,2,4-tricarboxylate

Cas Number:

3319-31-1

Molecular formula:

C33H54O6

IUPAC Name:

tris(2-ethylhexyl) benzene-1,2,4-tricarboxylate

Details on test material:

- Name of test material (as cited in study report): [Hexyl-2-14C] Tri-(2-ethylhexyl)trimellitate
- Physical state: liquid
- Radiochemical purity (if radiolabelling): ≥ 99%
- Specific activity (if radiolabelling): 4.83 mCi/mmol
- Locations of the label (if radiolabelling): 14C-labeled on the 2-carbon atom of the 2-ethylhexyl group

Radiolabelling:

yes

Remarks:

14C

Test animals

Species:

rat

Strain:

other: CD(SD) COBS

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratory, Wilmington, USA
- Weight at study initiation: 200-300 g
- Fasting period before study: rats were fasted 16 h prior to dosing.
- Housing: immediately after dosing, rats were placed in separate glass metabolism chambers equipped for the efficient separation of expired air, urine and faeces (Jencons, Hemel Hempstead, UK).
- Individual metabolism cages: yes
- Diet: Purina Rodent Laboratory Chow #5001 (Ralston Purina, St. Louis, USA), ad libitum
- Water: ad libitum

ENVIRONMENTAL CONDITIONS (GLASS METABOLSI CHAMBER)
- Humidity: dehumified air was drawn through the metabolic chamber at a rate of 500 mL/min

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Duration and frequency of treatment / exposure:

single administration

Doses / concentrations

Remarks:

Doses / Concentrations:
100 mg/kg bw (corresponding to approx. 16-18 µCi radioactivity per rat)

No. of animals per sex per dose / concentration:

4

Control animals:

no

Details on study design:

- Dose selection rationale: the test substance has a low risk for acute and subacute toxicity via the oral route. The oral LD50 value in rats was greater than 5000 mg/kg bw and rats gavaged with 1000 mg/kg bw for a period of 4 weeks did not provide any evidence for subacute toxicity.

Details on dosing and sampling:

PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: urine, faeces, expired air and organic compounds, tissues (brain, heart, lungs, liver, spleen, kidneys, small and large intestines, testes, abdominal fat) and carcass.
- Time and frequency of sampling: expired air was drawn through two silica gel traps to remove volatile 14C organic compounds and then through two alkali traps (2.5 M NaOH) to remove 14CO2. The silica gel traps were changed daily and the alkali traps were changed at frequent intervals up to 144 h post-administration. Urine and faeces were sampled 4, 8, 12, 24, 36, 48, 72, 96, 120 and 144 h after administration for analysis of radioactivity. At each collection period, the metabolism cages were rinsed with water. At the end of the experiment, cages were also rinsed with methanol followed by methylen chloride. Tissues and carcasses were obtained at sacrifice (144 h after administration) and analysed for radioactivity.
- Other: samples were analysed for radioactivity using a Tri-Carb Model 2660 Liquid Scintillation Spectrometer (Packard Instrument Co., Downers Grove, USA).

METABOLITE CHARACTERISATION STUDIES
- Tissues and body fluids sampled: urine and faeces
- Time and frequency of sampling: urine and faeces were sampled 4, 8, 12, 24, 36, 48, 72, 96, 120 and 144 h after administration for analysis of metabolites.
- From how many animals: 4
- Method type(s) for identification: radioactive compounds in faecal extracts were separated on a Dupont C18 analytical reverse phase column (Dupont Instruments, Wilmington, USA) using HPLC (Waters Assoc., Hilford, USA) coupled with an UV/VIS detector (Varian Instruments, Waltham, USA) and a radiochemical detector (Multirac® fraction collector (LKB, Bromma, Sweden)). The extracts were analysed directly by HPLC using a 25 x 0.45 cm C18 column and a 10 min linear gradient from 50% water/methanol to 100% methanol. Urinary metabolites were analysed using GC/MS (Hewlett-Packard model HP5987A) after solvent extraction with diethyl ether. GC separations were performed on a 0.3 mm DB5 column (J &W Scientific. Rancho Cordova, USA) using a 130-300 °C temperature gradient (10 °C/min).

Statistics:

Where appropriate, results were analysed by the Student’s test and values of p < 0.05 were considered significant.

Results and discussion

Main ADME results

Main ADME results 1

Type:

absorption

Results:

radioactivity from [Hexyl-2-14C] Tri-(2-ethylhexyl)trimellitate was only partly absorbed from the gastrointestinal tract after hydrolysis

Main ADME results 2

Type:

distribution

Results:

less than 0.6% remained in the tissues and carcass; thereof, most of the radioactivity was found in liver and adipose tissues

Main ADME results 3

Type:

metabolism

Results:

[Hexyl-2-14C] Tri-(2-ethylhexyl)trimellitate was only partly hydrolised in the gastrointestinal tract to di- and monoesters of trimellitic acid and 2-ethylhexanol and 2-ethylhexanol, which was largely oxidatively metabolised to 14CO2

Main ADME results 4

Type:

excretion

Results:

75.6% was excreted unchanged and as metabolites via faeces, 16.3% was excreted in the urine as metabolites, 1.9% was expired as 14CO2 and 0.03% was expired as volatile organics

Main ADME results 5

Type:

other: overall recovery of radioactivity

Results:

94.4%

Toxicokinetic / pharmacokinetic studies

Details on absorption:

Radioactivity from [Hexyl-2-14C] Tri-(2-ethylhexyl)trimellitate was only partly absorbed from the gastrointestinal tract after hydrolysis into di- and monoesters of trimellitic acid and 2-ethylhexanol and 2-ethylhexanol. Hydrolytic evidence indicated than only 2-ethylhexanol and the monoester of trimellitic acid with 2-ethylhexanol were absorbed.

Details on distribution in tissues:

Less than 0.6% remained in the tissues and carcass (see Table 1 under “Any other information on results incl. tables”), whereby most of the radioactivity was found in liver and adipose tissues. In comparison to the average concentration of radioactivity found in the carcass, concentrations of radioactivity in adipose tissue and liver were 3- and 5-fold increased, respectively.

Transfer into organs

Observation:

slight transfer

Remarks:

into liver and abdominal fat

Details on excretion:

75% of the administered dose of [Hexyl-2-14C] Tri-(2-ethylhexyl)trimellitate was excreted via faeces (see Table 1 under “Any other information on results incl. tables”). Thereof, 64% was recovered unchanged and 11% was recovered as metabolites. 16% of the dose was excreted in the urine as metabolites, 1.9% was expired as 14CO2 and 0.03% was expired as volatile organics. The rate of production of expired 14CO2 seemed to depend on the systemic concentration of [14C]2-ethylhexanol, which was a function of both its rate of absorption from the gastrointestinal tract and its rate of elimination via metabolism. Therefore, changes in the rate of excretion of 14CO2 provided insight into absorption processes. Peak rates of excretion for expired 14CO2 were observed after 2-3 hours and at 8-12 hours after dosing. The initial increase in the rate of production of 14CO2 presumably involved the hydrolysis of [Hexyl-2-14C] Tri-(2-ethylhexyl)trimellitate to 2-ethylhexanol and a diester of trimellitic acid and 2-ethylhexanol. The peak rate of excretion of 14CO2 between 8-12 hours was directly related to the amount of diester excreted via the faeces. Thus, the rate of excretion of expired 14CO2 over this interval was in part dependent on the extent to which the radiolabeled test substance was converted to di(2-ethylhexyl)trimellitate in the gut.

Toxicokinetic parameters

Toxicokinetic parameters 1

Toxicokinetic parameters:

half-life 1st: of 14CO2: 3.1 h

Toxicokinetic parameters 2

Toxicokinetic parameters:

half-life 2nd: of 14CO2: 31 h

Toxicokinetic parameters 3

Toxicokinetic parameters:

half-life 1st: of elimination via urine: 3.1

Toxicokinetic parameters 4

Toxicokinetic parameters:

half-life 2nd: of elimination via urine: 42 h

Metabolite characterisation studies

Metabolites identified:

yes

Details on metabolites:

In the gastrointestinal tract, [Hexyl-2-14C] Tri-(2-ethylhexyl)trimellitate was hydrolysed into diesters of trimellitic acid and 2-ethylhexanol and 2-ethylhexanol. The diester of trimellitic acid and 2-ethylhexanol was further hydrolysed to a monoester and 2-ethylhexanol. There is evidence than only 2-ethylhexanol and the monoester of trimellitic acid and 2-ethylhexanol (mono-(2-ethylhexyl)trimellitate) were absorbed. These was supported by the fact that only these metabolites and metabolites of 2-ethylhexanol (2-ethylhexanoic acid and 2-heptanone) were recovered in the urine.
The major part of radioactivity in faeces was identified as the unchanged radiolabeled substance (85.6%), and the metabolites di-(2-ethylhexyl)trimellitate (6.8%) and mono-(2-ethylhexyl)trimellitate (1.1%). The remaining radioactivity was attributed to unidentified polar metabolites (6.5%) (see Table 2 under “Any other information on results incl. tables”).
The analysis of urine from treated rats provided no evidence for phase I metabolism of the identified trimellitic acid esters. Thus, it would seem that that all of the radioactivity in expired air arose from the metabolism of [14C]2-ethylhexanol and not from the oxidative metabolism of trimellitic acid esters.

Any other information on results incl. tables

Table 1. Recovery of radioactivity from male rats dosed with 100 mg/kg bw Tri-(2-ethylhexyl)trimellitate [percentage of dose]

Rat No.	Urine (a)	Faeces	Expired CO2	Expired volatile organics	Tissue and carcass	Total recovery
1	8.3	93.1	2.0	0.01	0.52	103.9
2	22.0	65.7	3.5	0.04	0.96	92.2
3	9.9	81.3	0.8	0.03	0.32	92.4
4	25.1	62.3	1.1	0.05	0.47	89.0
Mean ± SD	16.3 ± 8.5	75.6 ± 14.3	1.9 ± 1.2	0.03 ± 0.02	0.57 ± 0.28	94.4 ± 6.5

SD = standard deviation; (a) values included cage wash

Table 2. HPLC analysis of faecal extracts from rats dosed with [Hexyl-2-14C] Tri-(2-ethylhexyl)trimellitate (a)

Retention time [min]	Proposed structure (b)	Percentage of radioactivity [%] (c)
8.2	mono-(2-ethylhexyl)trimellitate (monoester of trimellitic acid with 2-ethylhexanol)	1.1 ± 0.8
11.1	isomers of di-(2-ethylhexyl)trimellitate (diester of trimellitic acid with 2-ethylhexanol)	6.8 ± 5.2
17.6	tri-(2-ethylhexyl)trimellitate (test substance, triester of trimellitic acid with 2-ethylhexanol)	85.6 ± 8.2

(a) Radioactive compounds were separated on a C-18 ODS reverse phase column.

(b) Structures were confirmed by GC/MS. Mass spectra were compared to authentic samples of isomeric mixtures of mono- and di-esters of trimellitic acid.

(c) Values are the % of radioactivity in acetone extract of faeces.

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): low bioaccumulation potential based on study results