Methyl 2-hexyl-3-oxocyclopentanecarboxylate

Endpoint summary

Description of key information

- Oral: NOAEL = 100 mg/kg bw/day (both sexes), based on data from a GLP compliant OECD 408 study with Hedione (MDJ) a structural analogue, which is considered the key study.

Key value for chemical safety assessment

Toxic effect type:

dose-dependent

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: oral

Type of information:

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

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The reliability score is based on read across and study is in accordance with OECD guideline and GLP.

Justification for type of information:

The oral repeated dose toxicity of DHIJ is based on read-across with Hedione (MDJ). The read across justification is presented in the Repeated dose toxicity endpoint summary and the accompanying files are attached there. The inclusion of the read-across justification in the endpoint summary is done for review purposes.

Reason / purpose for cross-reference:

read-across source

Key result

Dose descriptor:

NOAEL

Effect level:

>= 100 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Remarks on result:

not determinable due to absence of adverse toxic effects

Critical effects observed:

no

Conclusions:

Administration of dietary concentrations of 10, 50 and 100 mg/kg/day of DHIJ, based on the rsults of Hedione (MDJ) to Sprague-Dawley rats for up to 90 days did not result in any adverse, toxicological effects. The NOAEL (No Observable Adverse Effect Level) was 100 mg/kg/day.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

100 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

OECD 408 study, in compliance with GLP.

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

To cover the Annex VIII requirements for repeated dose toxicity, an OECD 422 study wat performed with DHIJ. As a more robust study is available, with an extensive number of parameters investigated and with a longer exposure duration, performed with a structural analogue (Hedione, MDJ) this study is included in the dossier from a precautionary principle. First the executive summary of the study with the analogue Hedione is presented, then the studies with DHIJ are presented and thereafter the read across justification.

 

Oral 90 day repeated dose toxicity study in rats with Hedione (MDJ; Key)

This study was designed to assess the potential toxicity of the test substance when administered orally, via dietary admixture, to Sprague-Dawley CD® rats (10/sex/group) at dose levels of 10, 50, and 100 mg/kg/day for a period of at least 3 months in accordance with OECD TG 408 and in compliance with GLP. Control animals (10/sex) received untreated standard laboratory diet. Clinical observations and body weight measurements were performed on all animals pretest and weekly during the study period. Ophthalmoscopic examinations were conducted on all animals pretest and at termination of the dosing period. Food consumption was evaluated weekly beginning one week prior to initiation of dosing. Test substance intake measurements were performed weekly beginning one week after initiation of dosing. Motor activity, functional observational battery and ophthalmology observations were performed pretest and during the twelfth week of dosing. After 3 months of treatment, haematology, coagulation and clinical chemistry evaluations were performed, surviving animals were euthanatized, selected organs were weighed and organ/body weight and organ/brain weight ratios calculated. Complete macroscopic postmortem examinations were performed on all animals, and histopathological evaluation of all tissues was conducted for animals in the 0 and 100 mg/kg/day groups.

Administration of dietary concentrations of 10, 50 and 100 mg/kg/day of the test substance to Sprague-Dawley rats for up to 90 days did not result in any adverse toxicological effects.

Therefore, the NOAEL (No-Observable-Adverse-Effect-Level) was 100 mg/kg/day.

 

Combined repeated dose toxicity study with the reproduction / developmental toxicity screening test in rats (Supporting)

In this combined repeated dose toxicity study, performed according to OECD 422 under GLP, the test item was administrated to Sprague Dawley rats via oral gavage at concentrations of 100, 300 and 1000 mg/kg body weight/day. The males were treated for two weeks pre-mating, during mating and up to the day before sacrifice during the post-mating period (total of 36 days of treatment). The females were treated for a two week pre-mating period, during mating, pregnancy (gestation) and up to lactation day 13. Females (dams) were sacrificed on lactation day 14 after overnight fasting. All the main and recovery group animals were observed once daily for clinical signs, twice daily for mortality and morbidity, weekly once for detailed clinical examination, body weight and feed consumption. The main group females were observed additionally for body weight and feed consumption. Ophthalmological examination was carried out once before treatment for all animals, during end of the dosing period for main group males, during end of the lactation period (lactation day 13) for vehicle control and high dose group animals and during end of the recovery period for all the recovery group animals. Neurological/functional examination was performed for five randomly selected animals from each main group (towards the end of dosing period for males and on lactation day 13 for females) and towards the end of the recovery period for all recovery group animals. Clinical pathology (haematology and clinical chemistry) examinations were conducted for five randomly selected animals of both sex from main groups and urinalysis for five randomly selected main group males and from all recovery group animals on the day of necropsy. The serum collected at termination from main group males was subjected to serum thyroxine hormone (T4) levels estimations. The gross pathology and organ weighing was performed on the day of termination for all the main and recovery group animals. Histopathological examination was conducted on all the tissues collected from vehicle control and high dose main group animals (with special emphasis on stages of spermatogenesis in the male gonads and histopathology of interstitial testicular cell structure) sacrificed at termination.

All the tested dose main and recovery group animals did not reveal any clinical signs of toxicity and no mortality or morbidity was observed. No treatment related changes in body weight, percent change in body weight, feed consumption, ophthalmoscopic examination, neurological/functional examination, haematology, clinical chemistry, urinalysis (in main group males and recovery group animals), organ weights (both absolute and relative), thyroxine hormone levels (main group males) were observed in all the main and recovery group animals of either sex. No gross pathological changes were noted at all the tested and vehicle control dose group animals at termination. No treatment related histopathological findings were noted in all the high dose group animals (G4) during microscopic examination.

In conclusion, based on the absence of adverse effects at the highest concentration, the No Observed Adverse Effect Level (NOAEL) for parental toxicity is set on 1000 mg/kg body weight.

 

Repeated dose study in rats (Supporting)

In this dose range finding study based on OECD 407 (non-GLP) the test item was evaluated to determine the toxic potential when administered for a period of 14 consecutive days by oral (gavage) route to Sprague Dawley rats. This study was conducted to generate information on health hazards likely to arise from repeated exposure to the test substance for a period of 14 days and to select the doses for subsequent toxicity studies. A total of 40 (20 males + 20 females) Sprague Dawley rats were distributed to four groups. Each group (G1, G2, G3 and G4) consisted of 5 males and 5 females. The animals in G1 group were administered with vehicle (corn oil), the animals in G2, G3 and G4 groups were administered with test item Dihydro Isojasmonate at the dose levels of 100, 300 and 1000 mg/kg body weight/day, respectively. The vehicle and test item formulations were administered at a dose volume of 10 mL/kg body weight. Freshly prepared test item formulations were administered to the animals as soon as possible after preparation. All animals were observed for clinical signs, mortality and morbidity, detailed clinical examination. Weekly body weight and feed consumption was recorded. Ophthalmological examination was carried out during week 2 for all group animals. Haematology, clinical chemistry analysis, urinalysis and gross pathology were performed on day 15 for all group animals of both sexes.

The animals did not reveal any clinical signs of toxicity throughout the treatment and no mortality or morbidity was observed throughout the experimental period. No treatment related changes in body weight, percent change in body weight, feed consumption, ophthalmoscopic examination, haematology, clinical chemistry and urinalysis were observed. There were no gross pathological changes observed at any of the doses tested in either sex.

In conclusion, based on the results discussed, the No Observed Adverse Effect Level (NOAEL) of the test item was found to be 1000 mg/kg body weight/day (high dose) when administered for a period of 14 consecutive days by oral (gavage) to Sprague Dawley rats under the experimental conditions and the doses employed.

 

Read-across justification

To conclude on the developmental and repeated dose toxicity of DHIJ, read-across was performed to an OECD 414 study for a structural analogue Hedione. To justify that read-across from Hedione is scientifically robust, a high level of similarity between both substances was demonstrated.

The structural differences are limited to the number of carbon atoms in two side chains, and there are no differences in the functional groups present. The physicochemical properties of the substances are therefore very similar. Except for the water solubility of Hedione, which is significantly higher.This increases the absorption potential of Hedione.Based on the physicochemical properties it can be concluded that DHIJ will be absorbed similarly compared to Hedione. The distribution and metabolic pathways are considered to be the same for both substances because of similar LogKow values and structural similarities. In conclusion, the ADME processes are expected to be highly comparable between target and source substances.

The available toxicological data indicated that both substances have a similar toxicological profile. The acute oral toxicity potential is the same for both substances; LD50> 5000 mg/kg bw and no treatment related clinical signs were observed. The acute dermal toxicity potential is for both substances the same; LD50> 5000 mg/kg bw. However, animals receiving DHIJ showed adverse clinical signs as in diarrhoea and mucous in the stool. Necropsy indicated that these animals were suffering from dark liver, brown anogenital exudate, bloated intestines. These effects were not observed in the study for Hedione. As the tested dose, at which these clinical signs and necropsy were observed, is well above the minimal concentration level for classification (≤ 2000 mg/kg bw) it is not considered to have an impact on the read-across between both substances.

Both substances are considered to be not irritating/corrosive to the skin and eye. Both substances are considered to be not sensitizing to the skin. The NOAEL for repeated dose toxicity was for both substances placed at the highest dose level in absence of adverse effect. The highest dose tested was for Hedione limited to 100 mg/kg bw, while the highest dose for DHIJ is 1000 mg/kg bw/day. Nonetheless, the toxicological profile for repeated dose toxicity is considered to be the same. Both substances are not considered to be genotoxic based on several in vitro and in vivo tests performed. These findings were supported by similar structural alerts found in the OECD toolbox. For both substances no structural alerts were found for precedent reproductive and developmental toxic potential using the ‘DART scheme’ profiler.

In conclusion, the source and target substance have similar structures and have very similar physicochemical properties, a similar toxicological profile are not considered to have differences in ADME parameters. Therefore, read-across between both substances is scientifically justified and in accordance with Regulation (EC) no 1907/2006, Annex XI, 1.5.

 

In the OECD 422 study, a treatment related reduction in the percentage body weight change was observed during lactation on PND 1 to 4 and PND 4 to 7. During gestation, a treatment related reduction in feed consumption was observed during GD 7 to 14. In the absence of any other evidence of parental toxicity, these observations were not considered to be adverse. No treatment related effects were observed for all other parameters tested when tested up to the highest dose of 1000 mg/kg bw. Also in the 14-day dose range finding study based on OECD 407 no adverse effects were observed when tested up to a dose of 1000 mg/kg bw.

Also for Hedione, no adverse effects were observed up to the highest dose of 100 mg/kg bw following dietary administration of the test article for 90 days. This means that the NOAEL for repeated dose toxicity was for both substances placed at the highest dose level in absence of any adverse effect. Although this is not at the same dose for both substances, the toxicological profile for repeated dose toxicity is considered to be the same.

When taken all three repeated dose toxicity studies together, the 90-day study with Hedione should be considered the key study for derivation of the DNELs. This study is a robust study with an extensive number of parameters investigated and with the longest exposure duration. In the OECD 422, the animals were treated for a maximum of approximately 50 days, which means that the dosage period of the OECD 408 with Hedione, was almost twice as long. From a precautionary principle, the NOAEL of 100 mg/kg bw is also considered to be the most conservative approach and therefore, this value was selected as the starting point for the derivation of the DNELs.

For repeated dose toxicity, the 90-day study with Hedione, is considered to be the key-study for the derivation of the DNELs for DHIJ, since it is the study with the longest exposure duration and it is considered to be the most conservative approach to use the NOAEL of this sub-chronic study. In addition, it is considered appropriate in the light of the adoption of the NOAELs for maternal and developmental toxicity from Hedione.

 

As a worst case approach the NOAEL of 100 mg/kg bw/day, derived for toxicity in the OECD 408 study performed with Hedione, was selected as a starting point for the following DNELs derived:

-     DNEL Workers – inhalation systemic – long-term

-     DNEL Workers – dermal systemic – long-term exposure

-     DNEL General population – inhalation systemic – long-term exposure

-     DNEL General population – dermal systemic – long-term exposure

-     DNEL General population – oral systemic – long-term exposure

Justification for classification or non-classification

Based on the available information classification for STOT RE is not warranted in accordance with EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation No. 1272/2008.