Tangor, Murcote, ext.

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

not reported

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Old study but a lot of details available. Due to the read-across purpose it was given a Klimisch 2 rating, in accordance with the ECHA Practical guide #6 on the reporting of read-across in IUCLID. The justification for read across is provided in the attached background material of the chapter summary.

Cross-reference

Reason / purpose for cross-reference:

read-across: supporting information

Reference

Endpoint:

basic toxicokinetics in vivo

Type of information:

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

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Old study but a lot of details available. Due to the read-across purpose it was given a Klimisch 2 rating, in accordance with the ECHA Practical guide #6 on the reporting of read-across in IUCLID. The justification for read across is provided in the attached background material of the chapter summary.

Justification for type of information:

The read across is primarily based on limonene (> 25%), and to a lesser extent also on β-pinene, γ-terpinene and citral (all max 35%). There are no other major constituents ≥ 10% (with the exception of some qualities of lime oil where maximum values may be up to 22%). Although this threshold for limonene and the other constituents can be considered arbitrary, it is clear that the lower the limonene content, the more difficult read across for some endpoints is. In this category, read across was feasible because 1) the citrus NCSs did not only share limonene as a major constituent in a percentage >25%, but 2) citrus NCSs with a lower content of limonene also share β-pinene and/or γ-terpinene and or citral in the same range (max 35%%) and 3) there were no other major constituents ≥ 10% (except for lime oil). The latter criterion is also important because it excludes the addition of constituents which are uncommon to this citrus category and may hamper read across. For Lime oil some constituents are > 10%, but they do not alter the C&L and therefore can also be considered not hampering read across.
Based on the fact that the citrus NCSs share the same constituents and all contain one major constituent (D-limonene) and since physico-chemical properties are similar, there is no reason to expect any differences in toxicokinetic behaviour among the category members.

See also the attached justification

Reason / purpose for cross-reference:

read-across source

Preliminary studies:

In Igimi H. and Nishimura M. (1974) Studies on the metabolism of d-limonene (p-mentha-1,8-diene) I. The absorption, distribution and excretion of d-limonene in rats, Xenobiotica, vol 4(2), 77-84: the absorption, distribution and excretion of d-limonene were investigated in rats. About 60% of administered radioactivity was recovered in urine, 5% from faeces and 2% from expired CO2 within 48h. In bile duct cannulated rats, about 25% of the dose was escreted in bile within 24h.
In Kodama R., Noda K. and Ide H. (1974) Studies on the metabolism of d-limonene (p-mentha-1,8-diene) II. The metabolic fate of d-limonene in rabbits, Xenobiotica, Vol 4 (2), 85-95: following oral administration to 3 male rabbits, about 72% and 7% of the dose was excreted in urine and faeces during 72 hours respectively.

Type:

excretion

Type:

metabolism

Details on absorption:

rapid and almost complete on the basis of the urinary excretion level, with most excretion occuring within the first 24 hours.
In the case of man, absorption may also be rapid and complete as the urinary excretion was about 85% during 48 hours (about 80% within 24 hours) in subject 1 (relatively low urinary excretion in subject 2 might be due to diarrhoea which occurred at 2 hours after administration).

Details on excretion:

The main route of excretion of d-limonene was via urine, 75-95% of administered radioactivity being excreted in the urine during 2-3 days.
Faecal excretion amounted to less than 10% in animals during 2-3 days.

Metabolites identified:

yes

Details on metabolites:

The reactions in the d-limonene biotransformation include the oxidation of methyl groups to hydroxyl and further to carboxylic acid derivatives, hydroxylation at the C-6 position, oxidation at the 8,9-double bond, and glycine and glucuronide conjugation. Hydroxylation at the C-6 position leads to the formation of p-mentha-1,8-dien-6-ol (M-X).
The 8,9-diol metabolites such as M-II and M-IV are likely to be derived through the epoxide intermediate. The structure of 2-hydroxy-p-menth-8-en-7-oic acid (M-VII) can be derived by hydration of the 1,2-double bond of perillic acid (M-III).
The major metabolite of d-limonene in the urine was M-IV in rat and rabbit, M-IX in hamster, M-II in dog and M-VI in guinea pig and man.

List of the metabolites of d-limonene:

M-I: p-mentha1,8 -dien-10 -ol

M-II: p-menth-1-ene-8,9 -diol

M-III: perillic acid

M-IV: perillic acid-8,9 -diol

M-V: p-mentha-1,8 -dien-10 -yl-beta-D-glucopyranosiduronic acid

M-VI: 8 -hydroxy-p-menth-1 -en-9 -yl-beta-D-glucopyranosiduronic acid

M-VII: 2 -hydroxy-p-menth-8 -en-7 -oic acid

M-VIII: perillylglycine

M-IX: perillyl-beta-D-glucopyranosiduronic acid

M-X: p-mentha-1,8 -dien-6 -ol

M-XI: p-menth-1 -ene-6,8,9 -triol

Conclusions:

Interpretation of results: no bioaccumulation potential based on study results
The rate and amount of urinary excretion in rat, rabbit, hamster, guinea pig, dog and man suggest rapid elimination with no significant accumulation of compounds related to d-limonene in these species.

Executive summary:

The excretion and metabolism of d-limonene was studied in various species (rat, rabbit, hamster, guinea pig, dog and human after one oral administration (gavage or capsule according to species). Excretion was measured in urine and/or faeces during 2 to 3 days after administration.

Up to 11 metabolites were isolated and characterized.

The main route of elimination of d-limonene administered orally was via the urine in animals and man, 75 -95% of the administered radioactivity being excreted in the urine during 2 -3 days. Faecal excretion accounted for less than 10% of the dose in animals during 2 -3 days.

Data source

Reference

Reference Type:

publication

Title:

Studies on the metabolism of d-limonene (p-mentha-1, 8-diene). IV Isolation and characterisation of new metabolites and species differences in metabolism

Author:

Kodama R, Yano T, Furukawa K, Noda K and Ide H

Year:

1976

Bibliographic source:

Xenobiotica, vol. 6(6), 377-389

Materials and methods

Objective of study:

other: excretion and metabolism

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

The metabolism of d-limonene was investigated in various animal species. Isolation and characterisation of several metabolites was done.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

p-mentha-1,8-diene

IUPAC Name:

p-mentha-1,8-diene

Details on test material:

- Locations of the label (if radiolabelling): on the 9 position

Radiolabelling:

yes

Test animals

Species:

other: rat, hamster, guinea-pig, rabbit, dog

Strain:

other: Wistar, Syrian, Hartley, albino, mongrel

Sex:

male

Administration / exposure

Route of administration:

other: oral gavage for rat, rabbit, hamster and guinea pig; oral capsule for dog and human

Duration and frequency of treatment / exposure:

one administration only

Doses / concentrations

Remarks:

Doses / Concentrations:
800 mg/kg bw: rat, guinea pig, hamster and rabbit
400 mg/kg bw: dog
1.6 g: human (57 and 60 kg bw)

No. of animals per sex per dose / concentration:

3 rats, 3 guinea pigs, 4 hamsters, 3 rabbits, 2 dogs and 2 human beings

Control animals:

no

Details on dosing and sampling:

For the excretion study and quantitative determination of acidic urine metabolites, [14C]d-limonene was administered orally.
For quantitative determination of neutral urine metabolites, non-labelled d-limonene was administered to another group of animals.
Animals were placed in metabolism cages, and urine and faeces were collected separately during 2 to 3 days.
Humans took the compound in hard gelatin capsules with water, and urine only was collected during 2 days.

Results and discussion

Preliminary studies:

In Igimi H. and Nishimura M. (1974) Studies on the metabolism of d-limonene (p-mentha-1,8-diene) I. The absorption, distribution and excretion of d-limonene in rats, Xenobiotica, vol 4(2), 77-84: the absorption, distribution and excretion of d-limonene were investigated in rats. About 60% of administered radioactivity was recovered in urine, 5% from faeces and 2% from expired CO2 within 48h. In bile duct cannulated rats, about 25% of the dose was escreted in bile within 24h.
In Kodama R., Noda K. and Ide H. (1974) Studies on the metabolism of d-limonene (p-mentha-1,8-diene) II. The metabolic fate of d-limonene in rabbits, Xenobiotica, Vol 4 (2), 85-95: following oral administration to 3 male rabbits, about 72% and 7% of the dose was excreted in urine and faeces during 72 hours respectively.

Main ADME results

Main ADME results 1

Type:

excretion

Main ADME results 2

Type:

metabolism

Toxicokinetic / pharmacokinetic studies

Details on absorption:

rapid and almost complete on the basis of the urinary excretion level, with most excretion occuring within the first 24 hours.
In the case of man, absorption may also be rapid and complete as the urinary excretion was about 85% during 48 hours (about 80% within 24 hours) in subject 1 (relatively low urinary excretion in subject 2 might be due to diarrhoea which occurred at 2 hours after administration).

Details on excretion:

The main route of excretion of d-limonene was via urine, 75-95% of administered radioactivity being excreted in the urine during 2-3 days.
Faecal excretion amounted to less than 10% in animals during 2-3 days.

Metabolite characterisation studies

Metabolites identified:

yes

Details on metabolites:

The reactions in the d-limonene biotransformation include the oxidation of methyl groups to hydroxyl and further to carboxylic acid derivatives, hydroxylation at the C-6 position, oxidation at the 8,9-double bond, and glycine and glucuronide conjugation. Hydroxylation at the C-6 position leads to the formation of p-mentha-1,8-dien-6-ol (M-X).
The 8,9-diol metabolites such as M-II and M-IV are likely to be derived through the epoxide intermediate. The structure of 2-hydroxy-p-menth-8-en-7-oic acid (M-VII) can be derived by hydration of the 1,2-double bond of perillic acid (M-III).
The major metabolite of d-limonene in the urine was M-IV in rat and rabbit, M-IX in hamster, M-II in dog and M-VI in guinea pig and man.

Any other information on results incl. tables

List of the metabolites of d-limonene:

M-I: p-mentha1,8 -dien-10 -ol

M-II: p-menth-1-ene-8,9 -diol

M-III: perillic acid

M-IV: perillic acid-8,9 -diol

M-V: p-mentha-1,8 -dien-10 -yl-beta-D-glucopyranosiduronic acid

M-VI: 8 -hydroxy-p-menth-1 -en-9 -yl-beta-D-glucopyranosiduronic acid

M-VII: 2 -hydroxy-p-menth-8 -en-7 -oic acid

M-VIII: perillylglycine

M-IX: perillyl-beta-D-glucopyranosiduronic acid

M-X: p-mentha-1,8 -dien-6 -ol

M-XI: p-menth-1 -ene-6,8,9 -triol

Applicant's summary and conclusion

Conclusions:

Interpretation of results: no bioaccumulation potential based on study results
The rate and amount of urinary excretion in rat, rabbit, hamster, guinea pig, dog and man suggest rapid elimination with no significant accumulation of compounds related to d-limonene in these species.

Executive summary:

The excretion and metabolism of d-limonene was studied in various species (rat, rabbit, hamster, guinea pig, dog and human after one oral administration (gavage or capsule according to species). Excretion was measured in urine and/or faeces during 2 to 3 days after administration.

Up to 11 metabolites were isolated and characterized.

The main route of elimination of d-limonene administered orally was via the urine in animals and man, 75 -95% of the administered radioactivity being excreted in the urine during 2 -3 days. Faecal excretion accounted for less than 10% of the dose in animals during 2 -3 days.