Exo-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ol

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

publication

Title:

In Vitro Characterization of Borneol Metabolites by GC–MS Upon Incubation with Rat Liver Microsomes

Author:

Zhang R

Year:

2008

Bibliographic source:

Journal of Chromatographic Science, Vol. 46, May/June 2008, pp 419-423

Materials and methods

Objective of study:

metabolism

Principles of method if other than guideline:

- Principle of test: Study of metabolism of Borneol by the analysis of incubations of in vitro-prepared rat liver microsomes
- Short description of test conditions: see description below
- Parameters analysed / observed: Metabolites of Borneol in rat liver microsomes.

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

DL-borneol

EC Number:

208-080-0

EC Name:

DL-borneol

Cas Number:

507-70-0

Molecular formula:

C10H18O

IUPAC Name:

1,7,7-trimethylbicyclo[2.2.1]heptan-2-ol

Radiolabelling:

no

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Experimental Animal Center of Guangdong Province, P.R. China
- Age at study initiation: ca. 50 days
- Weight at study initiation: 230–250 g
- Housing: steel cages
- Diet (e.g. ad libitum): control diet
- Water (e.g. ad libitum): control diet
- Acclimation period: 1 week

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22–26°C
- Humidity (%): 50–60%

Administration / exposure

Route of administration:

other: In vitro incubation with rat liver microsomes

Details on exposure:

A typical incubation mixture consisted of 2.5 mg/mL rat liver microsmal protein, 0.1M potassium phosphate buffer (pH 7.4), 1mM Nicotinamide-adenine dinucleotide phosphate (NADPH), and 325μM Borneol with a final volume of 1 mL. Borneol was dissolved in methanol (final concentration in the reaction medium of < 1.0%).
The reaction was initiated by the addition of the NADPH, and then the oxygen was quickly added with a syringe needle going into the middle of the mixtures for 40 s.
Control incubations were performed using inactivated microsomes, which were boiled in 90°C water for 45 min.
After incubation in a shaking water bath at 37°C for 30 min, the reaction was terminated by adding 2 mL ethyl acetate. The mixture was extracted for 10 min by shaking vigorously and then centrifuged at 15,000 × g for 10 min.
The organic phases were directly injected into the Gas chromatography (GC)–Mass spectrometry (MS) for analysis.

Details on dosing and sampling:

METABOLITE CHARACTERISATION STUDIES
- Tissues and body fluids sampled: rat liver microsomes
- Method type(s) for identification: GC-MS

Results and discussion

Main ADME results

Type:

metabolism

Results:

Four metabolites (M1, M2, M3, and M4) were observed in the incubation mixture, which were not present in the control incubations

Metabolite characterisation studies

Metabolites identified:

yes

Details on metabolites:

Borneol was rapidly metabolized to four metabolites:
M1 (m/z 152): molecular weight of two mass units less than Borneol. M1 was confirmed as camphor by comparison with the standard mass spectrum library (NIST library, 95% similarity).
M2 (m/z 122): molecular weight of 32 mass units less than Borneol. It was proposed that this is the de-methylated and de-hydrated metabolite of Borneol. Although, further investigation is required to positively identify this metabolite.
M3 (m/z 170) and M4 (m/z 170): molecular weight of 16 mass units more than Borneol. it was proposed that M3 and M4 are probably hydroxylated metabolite(s) of borneol, although these will require further study to be certain.

Applicant's summary and conclusion

Conclusions:

Borneol was rapidly metabolized to four phase I metabolites in incubations with normal rat liver microsomes in the presence of NADPH.

Executive summary:

The metabolism of borneol was studied by the analysis of incubations of in vitro-prepared rat liver microsomes. Male Sprague-Dawley rats, aged approximately 50 days and weighing 230–250 g, were used for the study. A typical incubation mixture was performed in a shaking water bath at 37°C for 30 min and consisted of 2.5 mg/mL rat liver microsmal protein, 0.1M potassium phosphate buffer (pH 7.4), 1mM NADPH, and 325μM Bornel with a final volume of 1 mL. Gas chromatography (GC)–mass spectrometry (MS) method was developed for the identification of Borneol and its metabolites. Four phase I metabolites were detected: M1 (m/z 152) confirmed as camphor, M2 (m/z 122) proposed as the de-methylated and de-hydrated metabolite, M3 (m/z 170) and M4 (m/z 170) both proposed as the hydroxylated metabolites.