3,7-dimethyloct-6-en-1-yn-3-ol

Repeated dose toxicity: oral

Administrative data

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

10/11 March - 7/8 April 1992

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Study was conducted under GLP conditions and according to OECD guideline 407. 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. Linalool and Dehydrolinalool have almost identical chemical structures. The only difference is the triple bond at position 1 in Dehydrolinalool compared to a double bond at the same position in Linalool. Both substances have almost identical physical-chemical properties. Therefore, it is assumed that toxicological properties are as well comparable.

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

reference to same study

Cross-reference 2

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1992

Report date:

1992

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity Study in Rodents)

Deviations:

yes

Remarks:

Food consumption was not measured

Principles of method if other than guideline:

Not relevant

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

3,7-dimethyloct-6-en-1-yn-3-ol

EC Number:

249-482-6

EC Name:

3,7-dimethyloct-6-en-1-yn-3-ol

Cas Number:

29171-20-8

Molecular formula:

C10H16O

IUPAC Name:

3,7-dimethyloct-6-en-1-yn-3-ol

Details on test material:

- Name of test material (as cited in study report): dehydrolinalool
- Physical state: Liquid
- Molecular formula: C10H16O
- Molecular weight: 152.23
- SMILES Code: CC(=CCCC(C)(C#C)O)C
- InChI : 1/C10H16O/c1-5-10(4,11)8-6-7-9(2)3/h1,7,11H,6,8H2,2-4H3
- Stability under test conditions: Stable at room temperature
Emulsion in rape seed oil is stable at about 4°C for at least 3 weeks, fresh emulsions were prepared once a week.

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Biological Research Laboratories, CH-4414 Füllinsdorf, Switzerland
- Age at study initiation: approx. 6 weeks
- Weight at study initiation:
Males: 140-173 g
Females: 111-140 g
- Housing: 2 animals/cage, in stainless steel wire-mesh cages.
- Diet (e.g. ad libitum): pelleted complete rodent diet
- Water (e.g. ad libitum): ad libitum, tap water
- Acclimation period: 7 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): approx. 22
- Humidity (%): approx. 55
- Air changes (per hr): 20-25
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

other: rape seed oil

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:
Test article emulsified in rape seed oil

DIET PREPARATION
- Exposure not by diet (gavage)

VEHICLE
- Amount of vehicle (if gavage): 5 ml/kg bw

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

In week 1: After preparing the application solution and 1 week after storage at about 4 °C

Duration of treatment / exposure:

28 days

Frequency of treatment:

Daily, 7 days/week

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
Group 1: 200 mg/kg bw
Basis:
actual ingested

Doses / concentrations 2

Remarks:

Doses / Concentrations:
Group 2: 400 mg/kg bw 1st week, 600 mg/kg bw week 2 to 4
Basis:
actual ingested

Doses / concentrations 3

Remarks:

Doses / Concentrations:
Group 3: 900 mg/kg bw day 1-2, thereafter 1000 mg/kg bw
Basis:
actual ingested

No. of animals per sex per dose:

200/600 mg/kg/day: 10
Control/ 1000 mg/kg/day: 14 (4 animals intended for recovery period)

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Doses were selected referring to a feed-admix pilot study. At 900 mg/kg/day gastro-intestinal disorders were found in the pilot study. Therefore, the current study was started with this dose, but less apparent disorders were seen at gavage treatment. The dose was
increased to 1000 mg/kg/day (= limit dose according to OECD) after 2 days.

Positive control:

No

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily
- Cage side observations: clinical symptoms and mortality

BODY WEIGHT: Yes
- Time schedule for examinations: twice weekly during study and once weekly during recovery

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: Before study start and in week 4 (all animals) and 10 (recovery animals)

HAEMATOLOGY: Yes
- Time schedule for collection of blood: week 4 (all animals) and 10 (recovery animals)
- Anaesthetic used for blood collection: Yes (ether)
- Animals fasted: Yes, overnight
- How many animals: 10 animals/group and sex
- Parameters checked:
RBC (Red Blood Cells)
HB (Hemoglobin)
PCV (Packed Cell Volume, hematocrit)
MCV (Mean Corpuscular Volume)
MCH (Mean Corpuscular Hemoglobin)
MCHC (Mean Corpuscular Hemoglobin Concentration)
WBC (White Blood Cells)

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: week 4 (all animals) and 10 (recovery animals)
- Animals fasted: Yes, overnight
- How many animals: 10 animals/group and sex
- Parameters checked:

Centrifugal analyzer
AST (Aspartate aminotransferase)
AlT (Alanin aminotransferase)
ALP (Alkaline phosphatase)
CHS (Cholinesterase)
Ca (Calcium)
PI (Phosphorous)
TOBIL (Total bilirubin)
UREA
GLUC (Glucose)
TRIGL (Triglycerides)
TOCHO (Total cholesterol)
TOPRO (Total protein)

Electrophoresis of serum proteins
ALB (albumin)
AGLOB (alpha-globulins)
BGLOB (beta-globulins)
GGLOB (gamma-globulin)
A/G ratio

Ion-selective electrodes
Sodium(Na)
Potassium (K)

URINALYSIS: Yes
- Time schedule for collection of urine: week 3 (all animals) and week 10 (recovery animals)
- Metabolism cages used for collection of urine: Yes
- Animals fasted: Yes, but free access to water
- Parameters checked:
Colour
Specific gravity
pH
Protein
Glucose
Ketones
Bilirubin
Occult blood
Nitrite
Urobilinogen
Urinary sediment (light microscope)

Sacrifice and pathology:

GROSS PATHOLOGY: Yes, after necropsy determination of organ weights (adrenals, brain, heart, kidneys, liver, spleen, ovaries, testes)
HISTOPATHOLOGY: Yes, by fixation and staining (tissue: adrenals, aorta, bone/bone marrow, brain, cecum, colon, duodenum, epididymides,
esophagus, eyes, heart, intestinal lymph nodes, ileum, jejunum, kidneys, liver, lungs, ovaries, pancreas, pituitary gland, prostate, rectum, salivary
glands, sciatic nerve, seminal vesicle, skeletal muscle, skin (from the mammary area), spleen, stomach, testes, thymus, thyroid/parathyroid, trachea,
urinary bladder, uterus, pathological findings)

Other examinations:

Not relevant

Statistics:

- Mean ranks by Jonckheere test and Mann Whitney U-test
- Weight development by total weight gain and calculation of growth rate
- Organ weights by total weight adjusted organ weights

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

no effects observed

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not specified

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY
Two females of the high-dose group died showing increased salivation and sedation. A treatment-relationship could not be excluded. Symptoms related to gastro-intestinal intolerance were observed in all treated animals. These may be related to irritant properties of this test material. Also sedation was shown in high dose animals. These symptoms (hypersalivation and sedation) were considered to be compound-related.

BODY WEIGHT AND WEIGHT GAIN
Overall weight gain and growth rate of males of 1000 mg/kg/day group was about 10% lower compared to the control animals. Adverse effect of the high-dose cannot be excluded. Weight returned to normal after recovery.

ORGAN WEIGHTS
Both males and females of the mid and high dose groups showed an increased relative adjusted weight of the liver. After recovery this was less apparent. Slight effect on kidney weight was seen in male animals (mid- and high-dose).

GROSS- AND HISTOPATHOLOGY: NON-NEOPLASTIC
Major treatment-related changes were confined to the kidneys of the male animals. Dose-dependently increased tubular accumulation of hyaline droplets, was noted in nearly all treated males. Some effects were however also seen in control animals. Distinct hyalin droplets nephropathy was seen only in mid- and high-dose animals, with a clear trend towards reversibility.

Effect levels

Dose descriptor:

NOAEL

Effect level:

200 mg/kg bw/day (actual dose received)

Sex:

male/female

Basis for effect level:

other: Both sexes mid/high dose level: increase in relative liver weight Males mid /high dose level: increased relative liver weights and alpha2u-globuline nephropathy

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Linalool and Dehydrolinalool are liquids at room temperature and have a boiling point of 197 - 198°C. The slight differences in vapor pressure (Linalool: 0.27 hPa at 25°C, Dehydrolinalool: 0.11 hPa at 20°C), water solubility (Linalool: 1.56 g/L at 25°C, Dehydrolinalool: 2.45 g/L at 20°C), and log Pow (Linalool: 2.9 at 20°C, Dehydrolinalool: 2.61 at 25°C) are mainly the result of different testing temperatures. Vapor pressure favors evaporation, water solubility and logPow indicate that both substances may favor organic apolar environment.

Acute oral and dermal toxicity data reveal for both substances an LD50 of more than 2000 mg/kg bw. Acute inhalation toxicity was not tested by standard means. However, there were no deaths at a concentration of 3.2 mg Linalool/L and 1.0 mg Dehydrolinalool/L. Thus, the LC50s are greater than 3.2 mg Linalool/L and 1.0 mg Dehydrolinalool/L. Linalool and Dehydrolinalool are both skin and eye irritants as pure substances. Dilutions of 30% concentration and below for both substances show no eye irritant potential. Neither Linalool nor Dehydrolinalool showed sensitizing potential in human studies. It was shown that oxidation of Linalool should be prevented due to strong skin sensitising properties of the decomposition products.Therefore, Linalool is usually protected by antioxidants.

Overall, mutagenicity and genotoxicity testing was unremarkable. Both substances were negative in the Ames test and in an in vivo micronucleus test. Linalool was also negative in an in vitro chromosome aberration test and in an in vitro forward mutation testing. Although Dehydrolinalool was positive in the in vitro chromosomal aberration test in the absence of metabolic activation, the next higher Tier test i.e. the in vivo MNT in the bone marrow was clearly negative. 

Two repeated toxicity studies, 2 reprotoxicity screening studies, and a developmental toxicity study using gavage application for Linalool (either applied in coriander oil at 72.9% Linalool or as pure substance) and / or Dehydrolinalool showed the following consistent results: Histopathologically, male animals had alpha-2u-globulin nephropathy after application of both substances. Liver (and kidney) weights were increased in both sexes with some indication of metabolic enzyme induction in the liver. Hypersalivation and sedation / ataxia were consistently noted in almost all studies. In one oral study, gavage application resulted in (fore)stomach lesions which might be the result of the irritant properties. In a repeated dermal toxicity study, the skin irritant properties of Linalool were confirmed. The relevant oral NOAEL for Linalool was determined to be 117 mg/kg bw/d; Dehydrolinalool has an oral NOAEL of 200 mg/kg bw/d. The difference in the NOAELs is the result of the dose-setting regime. The NOAEL for dermal DNEL was 250 mg/kg bw/d.

Linalool (applied in coriander oil at 72.9% Linalool) was only tested for female fertility without showing an effect. Dehydrolinalool, however, was tested for male and female fertility and showed no adverse effect. Linalool was tested with regard to developmental toxicity / teratogenicity in two studies: screening test (applied in coriander oil at 72.9%) and full guideline compliant developmental toxicity study (pure substance). Both studies showed no evidence of adverse effects on foetuses and pups at doses which were not maternal toxic. Dehydrolinalool was also tested negative for this endpoint in a screening assay. From the data it is concluded that both substances are neither developmental toxic nor teratogenic at doses not being maternally toxic. However, at maternal toxic doses, reduced litter sizes and increased pup mortality was noted for both substances.

Applicant's summary and conclusion

Conclusions:

Dehydrolinalool is of low subacute toxicity in rats concerning hematological and clinical chemistry parameters. It induced treatment-related
hypersalivation (all dose groups) and sedation in the high-dose group. In males, dehydrolinalool induced hyaline droplet nephropathy at mid- and
high-dose levels.
This type of nephropathy is known to be specific in male rats with no predictive value for man. In both sexes of the mid and high dose group, relative adjusted liver weights were increased without histopathological correlate. In rats, 200 mg/kg/day is considered to be the
no-observed-adverse-effect-level (NOAEL).

Executive summary:

Dehydrolinalool was toxicologically investigated in rats for a period of 4 weeks. Doses of 0 mg/kg/d, 200 mg/kg/d, 600 mg/kg/d and 1000 mg/kg/d were given daily by oral gavage (400 mg/kg/d at the mid-dose in the first week, 900 mg/kg/d at the high-dose for 2 days). Each group consisted of 10 - 14 male and female Han WIST rats. Four animals per sex were allocated for recovery (43 days). The compound was administered as an emulsion in rape seed oil at a volume of about 5 ml/kg body weight, the controls received the same volume of rape seed oil. Extensive clinical, laboratory (hematology, clinical chemistry, urine) and pathology examinations were made in accordance with international guidelines (OECD, EC).

Clinical symptoms referring to gastro-intestinal intolerance (hypersalivation) were observed in all treated animals which may be related to irritant properties of the test material. At the high-dose some animals showed sedation. These symptoms are considered to be compound-related. Two females of the high-dose died spontaneously. Both deaths occurred in animals showing increased salivation and sedation. Five females (4 controls, 1 low-dose animal) died due to anemia shortly after bleeding. A slight, dose-related increase in the relative adjusted liver weight occurred in males and females of the mid- and high-dose level without histopathological correlate. The increase was less apparent after the recovery period. A slight increase in relative adjusted kidney weight was seen in mid- and high-dose males. Major treatment-related changes were confined to the kidney of the male animals. Tubular accumulation of hyaline droplets, with dose-dependent increase, were noted in nearly all treated males. However, similar severity of hyaline droplets accumulation was seen in 3 control males maintained up to termination of recovery and low-dose males sacrificed at treatment end. Distinct signs of tubular degeneration, which led to the diagnosis "hyaline droplets nephropathy" were seen only in males of the mid- and high-dose, with a clear trend towards reversibility. The hyaline droplet nephropathy is well known not to be relevant for human health.

It is concluded that dehydrolinalool is of low subacute toxicity in rats concerning hematological and clinical chemistry parameters. It induced treatment- related hypersalivation and sedation in the high-dose group. In males, dehydrolinalool induced hyaline droplet nephropathy at mid- and high-dose levels. This type of nephropathy is known to be specific in male rats with no predictive value for man. In rats, 200 mg/kg/d is considered to be the non-toxic dose.