(1S-endo)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ol

Endpoint summary

Link to relevant study record(s)

Reference

Reference 1

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

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

Radiolabelling:

no

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%

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

Type:

metabolism

Results:

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

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.

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.

Reference 2

Endpoint:

basic toxicokinetics in vitro / ex vivo

Type of information:

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

Adequacy of study:

weight of evidence

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
The analogue substance DL-Borneol which shares the same functional groups with the substance L-Borneol also has comparable values for the relevant molecular properties.
See attached the reporting format.

Reason / purpose for cross-reference:

read-across source

Metabolites identified:

yes

Details on metabolites:

Results based on read-across from analogue Borneol.
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.

Conclusions:

Based on the read-across approach from the analogue DL-Borneol, L-Borneol was determined to be 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. The read-across was applied and based on results of this study, L-Borneol was determined to have four phase I metabolites: 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.

Reference 3

Endpoint:

basic toxicokinetics in 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

Objective of study:

other: Obtaining of glycuronic acid through the feeding of borneol to dogs

Principles of method if other than guideline:

- Principle of test: preparation of glycuronic acid obtained through the excretion of borneol glycuronic acid after feeding dogs with borneol
- Short description of test conditions: see description below
- Parameters analysed / observed: Excretion of borneol glycuronic acid in urine

GLP compliance:

no

Radiolabelling:

no

Species:

dog

Strain:

not specified

Sex:

not specified

Details on test animals or test system and environmental conditions:

No data.

Route of administration:

oral: feed

Vehicle:

other: unchanged or suspended in gelatin glucose mixture

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
Borneol was incorporated directly with the food or suspended in a small volume of gelatin glucose mixture.

Duration and frequency of treatment / exposure:

Frequency of treatment: Daily

Dose / conc.:

5 other: g/day

Details on dosing and sampling:

TOXICOKINETIC / PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled (delete / add / specify): urine
- Time and frequency of sampling: daily

Type:

excretion

Results:

Approximately 50% of the daily dose of 5 g borneol was excreted in the urine as borneol glycuronic acid.

Metabolites identified:

no

Conclusions:

Approximately 50% of the daily dose of 5 g borneol in dogs was excreted in the urine as borneol glycuronic acid.

Executive summary:

Borneol at dose level of 5.0 g was incorporated directly with the food or suspended in a small volume of gelatin glucose mixture and fed daily to dogs. Approximately 50% of the daily dose of 5 g borneol was excreted in the urine as borneol glycuronic acid.

Reference 4

Endpoint:

basic toxicokinetics in vivo

Type of information:

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

Adequacy of study:

weight of evidence

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
The analogue substance DL-Borneol which shares the same functional groups with the substance L-Borneol also has comparable values for the relevant molecular properties.
See attached the reporting format.

Reason / purpose for cross-reference:

read-across source

Type:

excretion

Results:

Based on results from analogue borneol, about 50% of a daily dose of L-borneol to dogs is expected to be excreted in the urine as the glycuronic acid conjugate.

Metabolites identified:

no

Conclusions:

Based on the read-across approach from the analogue DL-borneol, about 50% of a daily dose of L-borneol to dogs is expected to be excreted in the urine as the glycuronic acid conjugate.

Executive summary:

Borneol at dose level of 5.0 g was incorporated directly with the food or suspended in a small volume of gelatin glucose mixture and fed daily to dogs. Approximately 50% of the daily dose of 5 g borneol was excreted in the urine as borneol glycuronic acid. The read-across was applied and based on results of this study, about 50% of a daily dose of L-borneol to dogs is expected to be excreted in the urine as the glycuronic acid conjugate.

Reference 5

Endpoint:

basic toxicokinetics in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

abstract

Objective of study:

metabolism

Principles of method if other than guideline:

- Principle of test: Study on the glucuronidation of various chemicals by human embryonic kidney 293 cells expressing UDP-glucuronosyltransferase 1.4 protein.
- Short description of test conditions: see description below
- Parameters analysed / observed: rate of glucuronidation.

GLP compliance:

not specified

Radiolabelling:

no

Species:

other: Human

Details on test animals or test system and environmental conditions:

embryonic kidney 293 cells (whole-cell homogenates) expressing UDP-glucuronosyltransferase 1.4 protein were used.

Route of administration:

other: In vitro incubation with embryonic kidney 293 cells

Details on exposure:

The assays were performed at 37ºC embryonic kidney 293 cells (whole-cell homogenates) expressing UDP-glucuronosyltransferase 1.4 protein.
The incubation time was 0.5-2 h.

Dose / conc.:

0.5 other: mM

Remarks:

Concentration of L-Borneol on incubation mixture

Details on dosing and sampling:

METABOLITE CHARACTERISATION STUDIES
- Tissues and body fluids sampled: Human embryonic kidney 293 cells

Type:

metabolism

Results:

The rate of glucuronidation of 0.5 mM l-borneol by human embryonic kidney 293 cells expressing UDP-glucuronosyltransferase 1.4 protein was 29 pmol/min/mg protein

Metabolites identified:

no

Conclusions:

The rate of glucuronidation of 0.5 mM L-borneol by human embryonic kidney 293 cells expressing UDP-glucuronosyltransferase 1.4 protein was 29 pmol/min/mg protein.

Executive summary:

The glucuronidation of L-Borneol by human embryonic kidney 293 cells expressing UDP-glucuronosyltransferase 1.4 protein was investigated. The assays were performed at 37ºC with a concentration of L-Borneol of 0.5 mM and an incubation time of 0.5-2 h. The rate of glucuronidation of L-Borneol was found to be 29 pmol/min/mg protein.

Description of key information

Weight of Evidence: Read-across approach. Based on the read-across approach from the analogue DL-Borneol, L-Borneol was determined to be rapidly metabolized to four phase I metabolites in incubations with normal rat liver microsomes in the presence of NADPH.

Weight of Evidence: Read-across approach. Based on the read-across approach from the analogue DL-Borneol, about 50% of a daily dose of L-Borneol to dogs is expected to be excreted in the urine as the glycuronic acid conjugate.

Weight of Evidence: In vitro human study on L-Borneol. The rate of glucuronidation of 0.5 mM L-borneol by human embryonic kidney 293 cells expressing UDP-glucuronosyltransferase 1.4 protein was 29 pmol/min/mg protein.

Additional information

Weight of evidence. Read-across approach from experimental data on the analogue substance DL-Borneol: 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. The read-across was applied and based on results of this study, L-Borneol was determined to have four phase I metabolites: 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.

Weight of Evidence: Read-across approach from experimental data on the analogue substance DL-Borneol: Borneol at dose level of 5.0 g was incorporated directly with the food or suspended in a small volume of gelatin glucose mixture and fed daily to dogs. Approximately 50% of the daily dose of 5 g borneol was excreted in the urine as borneol glycuronic acid. The read-across was applied and based on results of this study, about 50% of a daily dose of L-borneol to dogs is expected to be excreted in the urine as the glycuronic acid conjugate.

Weight of Evidence: In vitro human study on L-Borneol. The glucuronidation of L-Borneol by human embryonic kidney 293 cells expressing UDP-glucuronosyltransferase 1.4 protein was investigated. The assays were performed at 37ºC with a concentration of L-Borneol of 0.5 mM and an incubation time of 0.5-2 h. The rate of glucuronidation of L-Borneol was found to be 29 pmol/min/mg protein.