Registration Dossier

Toxicological information

Basic toxicokinetics

Currently viewing:

Administrative data

Endpoint:
basic toxicokinetics in vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
no data
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Data source

Reference
Reference Type:
publication
Title:
Transformations metaboliques de la trimethyl-3,5,5, cyclohexene-2, one-1 (isophorone)
Author:
Dutertre Catella H, Lich NP, Quan DQ and Truhaut R
Year:
1978
Bibliographic source:
Toxicol. Europ. Res. 1, 209-216
Report Date:
1978

Materials and methods

Objective of study:
metabolism
Principles of method if other than guideline:
other: metabolism study; method see reference
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Details on test material:
origin: Ugine-Kuhlmann ; purity > 99%
ca. 91.5 % alpha-isophorone, CAS-78-59-1
ca. 8.5 % beta-isophorone, CAS 471-01-2
traces 3,3,5-trimethylcyclohexanone, CAS 873-94-9

Remark: No distincion was made between alpha-isophorone, CAS-78-59-1 and  beta-isophorone, CAS 471-01-2
Radiolabelling:
no

Test animals

Species:
other: rabbits and rats
Strain:
other: rabbit: New Zealand White; rat: Wistar
Sex:
not specified
Details on test animals and environmental conditions:
TEST ORGANISMS
- Rabbits, New Zealand White
-Rats, Wistar
- Weight at study initiation:    rabbits ca. 2.5 kg; rats ca. 250 g
- Number of animals: not reported

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
other: rabbits: pure substance followed by ca. 20 ml water; rats: olive oil
Details on exposure:
ADMINISTRATION / EXPOSURE 
- Duration of test/exposure: single dose
- Type of exposure: gavage
- Post exposure period:    Air sampling for 6 hours after dosing; Urine sampling 24 and 48 hours after dosing  
- Vehicle:    rabbits: pure substance followed by ca. 20 ml water   rats: olive oil
- Concentration in vehicle: 0.2 g/ml (rats)
- Total volume applied: 1 ml/200 g bw (rats)
- Doses: 1000 mg/kg bw
SAMPLING
- Exhaled air (part of the animals): absorption on charcoal
- Urine sampling for 48 hours
Duration and frequency of treatment / exposure:
single dose
Doses / concentrations
Remarks:
Doses / Concentrations:
1000 mg/kg bw
No. of animals per sex per dose:
not reported
Control animals:
no
Positive control:
no positive control
Details on study design:
ANALYSIS
Urine: Enzymatic hydrolysis by beta-glucuronidase (buffered at pH 4.7, 37  °C), extraction, gas chromatography, identification using Kovats index
Charcoal: Elution with dichloromethane, gas chromatography,  identification using Kovats index
Details on dosing and sampling:
no details
Statistics:
not reported

Results and discussion

Preliminary studies:
not reported

Toxicokinetic / pharmacokinetic studies

Details on absorption:
not applicable
Details on distribution in tissues:
not applicable
Details on excretion:
Following oral administration of isophorone to rats and rabbits, the substance was partly eliminated unchanged in expired air and urine. The
remainder was metabolized to: see below

Metabolite characterisation studies

Metabolites identified:
yes
Details on metabolites:
Urine:  The following substances were identified both in rabbits and rats urine,  however in varying ratios:
- Unreacted isophorone
- 3,5,5-trimethylcyclohexan-1-one (dihydroisophorone - mainly in rats)
- 3,5,5-trimethyl-2-cyclohexen-1-ol (isophorol - mainly in rabbits)  eliminated as glucuronide
- 3,5,5-trimethylcyclohexan-1-ol (CAS 116-02-9), cis (933-48-2) and trans  (767-54-4) isomers. 
These compounds were identified only via GC and correlation to Kovats  indices.  Further compounds were seen, but could not be identified.

5,5-dimethyl-2-cyclohexen-1-one-3-carboxylic acid was extracted, isolated  and identified (GC, IR) in the urine of rabbits.
Expired air of rats and rabbits: unreacted isophorone

Any other information on results incl. tables

Fig. 1 Metabolic scheme for isophorone: see atteched document





Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): other: while part of the absorbed isophorone is excreted unchanged via urine and exhaled air, metabolites are mainly excreted as glucuronides
The main metabolite of rabbits after isophorone administration is  5,5-dimethyl-2-cyclohexene-1-one-3-carboxylic acid found as glucuronide  
conjugate in the urine (after 48 hours). Further detoxifications occur in rabbit and rat was hydrogenation of the 1-one-, the 2-ene- and both  
positions.
Executive summary:

Following oral administration of isophorone to rats and rabbits, the substance was partly eliminated unchanged in expired air and urine; the remainder was metabolized (see attached document) to:

a) 5,5 -dimethyl-cyclohex-1-en-3 -one-1-carboxylic acid (i), derived from isophorone by methyl-oxidation;

b) isophorol (3,5,5 -trimethyl-cyclohex-2 -en-1 -ol) (ii), formed by the reduction of the ketonic group to a secondary alcohol and eliminated as a glucuronide;

c) dihydroisophorone (3,5,5 -trimethyl-cyclohexanone) (iii), proceeding from the hydrogenation of the cyclohexene ring; and

d) cis- and trans-3,5,5 -trimethyl-cyclohexanol-1 (iv), likely to have formed from dihydroisophorone.

The amounts of the identified metabolites as a proportion of the administered dose were not reported. The metabolites were detected in the urine of rats and rabbits 24 and 48 hours after the administration. The expired air contained unchanged isophorone 6 hours after dosing.