4-tert-pentylcyclohexanone

Endpoint summary

Description of key information

Orivone systemic toxicity is derived from the analogue trans-4-tert-butyl cyclohexanol for which an oral gavage OECD TG 408 study was performed: NOAEL = 240 mg/kg bw/ day and a LOAEL at 800 mg/kg bw.

The systemic toxicity in an OECD TG 414 study with the analogue 4 -tert-butylcyclohexyl acetate (similar to OECD TG 414), with a NOAEL of 160 and a LOAEL 640 mg/kg bw, is derived.

The type of effects seen in the OECD TG 414 clinical signs, such as (excess) salivation quite severe decreases in body weight and food consumption are also seen in the OECD TG 408 study and indicate a similar mode of action. The sacrificed dam / 25 dams on day 20 of the OECD TG 414 study, can be the result of low body weight and being pregnant. This dam showed a similar pattern of body weight up to day 18 as other dams in this high dose group. At day 19 and 20 this dam had the lowest body weight, therefore the body weight decrease may be crucial here. Taking the decreased body weight as a key indicator for repeated dose toxicity we can assume that in absence of such body weight loss mortality will not occur either. Therefor the derived NOAEL from the OECD TG 414 study can be used as a starting point for sub-chronic repeated exposure because the exposure and effects during pregnancy are also covered.

Key value for chemical safety assessment

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: read-across from a guideline study

Justification for type of information:

The type of effects seen in the OECD TG 414 clinical signs, such as (excess) salivation quite severe decreases in body weight and food consumption are also seen in the OECD TG 408 study and indicate a similar mode of action. The sacrificed dam / 25 dams on day 20 of the OECD TG 414 study, can be the result of low body weight and being pregnant. This dam showed a similar pattern of body weight up to day 18 as other dams in this high dose group. At day 19 and 20 this dam had the lowest body weight, therefore the body weight decrease may be crucial here. Taking the decreased body weight as a key indicator for repeated dose toxicity we can assume that in absence of such body weight loss mortality will not occur either. Therefor the derived NOAEL from the OECD TG 414 study can be used as a starting point for sub-chronic repeated exposure because the exposure and effects during pregnancy are also covered.

Reason / purpose for cross-reference:

read-across source

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Sex:

female

Basis for effect level:

body weight and weight gain

clinical biochemistry

clinical signs

haematology

histopathology: non-neoplastic

organ weights and organ / body weight ratios

Remarks on result:

other: Result read-across source CAS No.21862-63-5

Remarks:

Correction for molecular weight not required

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Sex:

male

Basis for effect level:

body weight and weight gain

clinical biochemistry

clinical signs

haematology

histopathology: non-neoplastic

organ weights and organ / body weight ratios

Remarks on result:

other: Result read-across source CAS No.21862-63-5

Remarks:

Correction for molecular weight not required.

Dose descriptor:

LOAEL

Effect level:

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

Based on:

test mat.

Sex:

male

Basis for effect level:

histopathology: non-neoplastic

Remarks on result:

other: Result read-across source CAS No.21862-63-5

Remarks:

Correction for molecular weight not required

Key result

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Sex:

female

Basis for effect level:

body weight and weight gain

clinical signs

food consumption and compound intake

mortality

Remarks on result:

other: Result read-across source CAS No 32210-23-4

Remarks:

Effect level is corrected for the difference in molecular weight

Critical effects observed:

yes

Lowest effective dose / conc.:

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

System:

urinary

Organ:

kidney

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

no

Key result

Critical effects observed:

no

Conclusions:

The derived NOAEL for repeated dose toxicity is 240 mg/kg bw based on read across from para-tert-butyl cyclohexanol

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

136 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

For repeated dose toxicity one subchronic oral study is available, conducted according to OECD TG 408 in compliance with GLP and repeated dose toxicity information is available from a developmental toxicity (OECD TG 414), which present the quality of the database. .

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

The 90 -day repeated dose toxicity information for Orivone is derived from trans-4 -tert-butylcyclohexanol, a close analogue. First the repeated dose toxicity study is summarised below. Thereafter the read-across justification is presented. The accompanying files are attached here in the Repeated Endpoint summary.

The OECD TG 408 with trans-4 -tert-butylcyclohexanol used for read-across to Orivone:

In a sub-chronic study according to OECD TG 408 and GLP, Wistar rats RccHanTM: WIST(SPF were orally (gavage) exposed to 0, 80, 240 and 800 mg/kg bw/day for 90 days with a 28 days recovery period. The groups comprised 10 females and 10 males which were sacrificed after 91 and 92 days of treatment, respectively. Additional 5 rats per sex and group were used in the control group (treated with corn oil only), the vehicle group (treated with 10% ethanol in corn oil) and the high-dose group (treated with 800 mg/kg/day). Recovery animals were treated for 91 days, and then allowed a 28-day recovery period after which they were sacrificed. Viability/mortality, clinical signs, food consumption and body weights were recorded periodically during acclimatization, treatment and recovery. Weekly behavioural observations were performed during treatment. Functional observational battery, locomotor activity and grip strength tests were performed during week 13. At the end of the treatment period and the recovery period, blood samples were withdrawn for haematology and plasma chemistry analyses. Urine samples were collected for urinalyses. All animals were killed, necropsied and examined post mortem. Histological examinations were performed on organs and tissues from all animals of the control group (treated with corn oil only), the vehicle group (treated with 10% ethanol in corn oil) and the high-dose group. From the animals of the low and mid dose groups (treated with 80 and 240 mg/kg/day, respectively) liver, kidneys, stomach, prostate, nasal cavities and pharynx were examined in an attempt to establish a no-effect level. 

Results:Clinical effects: No substance related mortality, (neuro)behavioural or ophthalmoscopic effects were observed. Males and females in the high dose group showed slight to moderate dyspnea (short breath) and slight to moderate salivation, which was considered treatment related. Body weight and bodyweight changes were significantly reduced in the high dose group, which was not evident during the recovery period. Haematological effects were within the range of historical control data.

Liver related parameters: The observed changes in clinical biochemistry parameters except for triglyceride levels in females treated with 800 mg/kg/day and phospholipids and globulin levels in males treated with 800 mg/kg/day, were within the range of historical control data. These alterations were not evident after the 28 day recovery period. The relative liver weights were increased in mid and high dose males and in high dose females. Accentuated lobular pattern in livers of 2 and 3 males form the mid and high dose group, respectively, were observed.                                   

Kidney related parameters: Observed effects on urinalysis parameters were within the range of historical control data. The effects in the kidney in males can be contributed to alpha-hydrocarbon nephropathy. Relative kidney weights were increased in all doses in males. This increase in kidney weight in the high dose was still present after the recovery period. The effects consisted of increased incidence or incidence and severity of hyaline droplets, tubular basophilia and mononuclear cell foci along with granular casts and tubular dilation in all males. Hyaline casts were increased in incidence animals treated with 240 and 800 mg/kg/day, and tubular cysts were recorded in animals treated with 800 mg/kg/day. Some of these effects in the high dose males were still seen after the recovery period.

In high dose females an increase in incidence or incidence and severity of tubular basophilia along with minimal granular casts, tubular dilation and tubular cysts was observed. In recovery animals, increased incidences and severities of tubular basophilia, granular casts, mononuclear cell foci and tubular dilation along with increased incidence of hyaline casts were still recorded in males treated with 800 mg/kg/day.

Stomach related effects: The effects in the stomach represented a localized stomach reaction to a slightly irritant test item dosed repeatedly via gavage. There were minor incidences and/or severities of epithelial hyperplasia, hyperkeratosis, focal glandular erosion and forestomach ulceration in animals treated with 240 and 800 mg/kg/day. A number of findings recorded in the nasal cavity, nasopharyngeal duct and pharynx were deemed to be due to accidental uptake of the vehicle/test item by regurgitation.

Fertility: In the prostate, minimal focal or multifocal glandular inflammation, characterized by degenerating granulocytic cell infiltrates and inspissated colloid, were recorded in 3/10 males treated with 800 mg/kg/day.

In summary: The high dose 800 mg/kg presents systemic toxicity: decrease in body weight (gain), effects on liver, kidney and prostate. This dose seems to be the maximum tolerable dose. The kidney effects at the low and mid dose in males can be contributed toα2u-globulin nephropathy and is not relevant for human. Therefore the overall NOAEL (No-Observed-Adverse-Effect-Level) for effects relevant to human risk assessment is set at 240 mg/kg/day.

The overall conclusion of the developmental toxicity of para-tert-butyl cyclohexyl acetate (full summary is presented in the executive summary in the study record at the developmental toxicity section).

At the high dose of 640 mg/kg bw after dosing p-tert-butyl cyclohexyl acetate quite severe clinical signs, body weight and food reduction was seen, with one dam out of 25 that needed to be sacrificed on day 20. The next lower dose no such effects were seen. The maternal and developmental NOAEL were both 160 mg/kg bw/day. The maternal decrease in body weight and food consumption at the high dose resulted in transient delay of fetal development. These effects are therefore not considered to be selectively toxic to embryo-fetal development. 

Assessing repeated dose toxicity of Orivone (CAS#16587-71-6) using read-across form p-tert-butyl-trans-cyclohexanol (CAS# 21862-63-5) and multi-constituentp-tert-butyl cyclohexyl acetate (CAS# 32210-23-4)

1. Introduction and hypothesis for the analogue approach

Orivone (CAS# 16587-71-6) has a cyclohexanone backbone substituted with a (1,1)dimethyl-propyl moiety on thepara-position. For this substance no data on repeated dose toxicity are available.In accordance with Article 13 of REACH, lacking information should be generated whenever possible by means other than vertebrate animal tests, i.e. applying alternative methods such as in vitro tests, QSARs, grouping and read-across. For assessing the repeated dose toxicity of Orivone the analogue approach is selected because data are available on the related analogue p-tert-butyl-trans-cyclohexanol (CAS# 21862-63-5) andp-tert-butyl cyclohexyl acetate (CAS# 32210-23-4). The 90 days repeated dose study on p-tert-butyl-trans-cyclohexanol will be used. In view of the systemic toxicity being higher (lower NOAEL) in the developmental toxicity with p-tert-butyl cyclohexyl acetate theNOAEL of this study will be used for hazard assessment. 

Hypothesis: The systemic toxicity of Orivone (target) is the same as for p-tert-butyl-trans-cyclohexanol (source) andp-tert-butyl cyclohexyl acetate (source).

Available information: For Orivone only an acute oral toxicity study is available but no repeated dose toxicity.

For p-tert-butyl-trans-cyclohexanola well conducted 90-day repeated dose study with a 28 days recovery element is available (according to OECD TG 408, GLP and Kl 1). In this study doses up to 800 mg/kg bw/day were tested and a NOAEL of 240 mg/kg bw is obtained. At the high dose dyspnoea was seen. Body weights were decreased. Urinary volume was increased. Some blood parameters were affected: there was an increase in prothrombine time and decrease partial thromboplastin time. Reticulytes were affected in females. Blood lipid levels in females were increased (tryglycerides, phospholipids and globulin levels). Stomach showed irritation effects. Relative liver and kidney weight were increased.

For p-tert-butyl cyclohexyl acetate, a developmental toxicity study (similar to OECDT G 414, GLP and Kl 1) is available with the high doses of 640 mg/kg bw/day and a NOAEL of 160 mg/kg bw/ day for maternal systemic toxicity is obtained. The 640 mg/kg bw resulted in clinical signs, increase in salivation and decreased body weight. One out of 25 females after 20 days died in this study which was attributed to the substance.

2.Target chemical and source chemicals

Chemical structures and physico-chemical properties of the target source chemicals are presented in the data matrix

3. Purity / Impurities

The reported purity of the Orivone,p-tert-butyl-trans-cyclohexanol andp-tert-butyl cyclohexyl acetateis > 98%. For Orivone the major impurity identified iscis‐4‐(2‐methylbutan‐2‐yl)cyclohexanol, which is present at 1.6 % (relative peak area).The purity and impurities of the target chemical do not indicate repeated dose toxicity potential other than indicated by the parent substance.

4. Analogue approach justification

According to REACH Annex XI 1.5 read-across can be used to replace testing when the similarity can be based on a common backbone and a common functional group. When using read-across the result derived should be applicable for C&L and/or risk assessment and it should be presented with adequate and reliable documentation.

Analogue selection:Based on database searches (RIFM database and OECD QSAR Toolbox,p-tert-butyl-trans-cyclohexanol (CAS#21862-63-5)was identified as an analogue for which repeated dose toxicity is available. This analogue has, besides one less methyl group in the tail, an alcohol instead of a ketone.The second source substancep-tert-butyl cyclohexyl acetate (CAS#32210-23-4)can be used as an analogue too because the acetate group is metabolized to an alcohol.

Structural similarities and differences:The source and target substances have a common cyclohexane backbone with asubstituted tertiary-butyl moiety on the para-position. Orivone has one additional methyl group attached to the tertiary-butyl group. Considering functional groups: Orivone is substituted with a ketone, while thesource substances have an alcohol (p-tert-butyl-trans-cyclohexanol) or an acetate (p-tert-butyl cyclohexyl acetate).

Toxico-kinetic similarities and differences:AbsorptionThe molecular weight (168.3, 156.3 and 198.3 g/mol for Orivone,p-tert-butyl-trans-cyclohexanolandp-tert-butyl cyclohexyl acetate, respectively) and physico-chemical properties of Orivone and the source substances are in a similar range, indicating similar absorption characteristics.Metabolism: The ketone in Orivone and the alcohol inp-tert-butyl-trans-cyclohexanol are easily converted in each other by reduction or oxidation reactions. In addition, hydrolysis of the acetate moiety inp-tert-butyl cyclohexyl acetate will give the alcohol metabolitep-tert-butyl-cyclohexanol.

 

 

Fig 1. Metabolic pathways (Phase 1) of Orivone and p-tert-butyl cyclohexanol and its acetate

 

From an experimental study on structurally related tert-butyl cyclohexanones in rabbits, it appears that the 4-tert butyl ketones will be converted into their respective alcohols and that the cis/trans-conversion is 24/76. These alcohols are extensively conjugated to glucuronic acid prior to excretion (Cheo et al. 1967). Beside glucuronation the alcohols will be attached to alpha2u-globuline in the liver lysosomes because these globulins are precipitated in the male kidneys cause alpha2u globulin- hydrocarbon nephropathy. Oxidation of the tert-butyl tail may result in primary alcohols and carboxylic acids (not shown in Fig 1) for all substances.

Toxico-dynamicaspects: The substances are expected to have a similar toxicity profile. Since the ketone (in Orivone) and alcohol (present in in the source p-tert-butyl-trans-cyclohexanol and after the hydrolysis of p-tert-butyl cyclohexyl acetate) are easily converted in each other. At high doses , e.g. around 600 mg/kg bw, clinical signs and body weight decreases are anticipated as well as liver and kidney effects. The presence or absence of the methyl group in the alkyl tail of the molecules is not considered to change the reactivity of the molecule.

Experimental data other than repeated dose toxicity:The acute oral LD50 of Orivone and p-tert-butyl cyclohexyl acetate are in the same range: around 4000 mg/kg bw. The p-tert-butyl cyclohexanol and p-tert-butyl cyclohexyl acetate show clinical signs and body weight decrease after high repeated exposure in the OECD TG 408 (800 mg/kg bw) and OECD TG 414 (640 mg/kg bw), respectively. The Ames test is negative for all three substances. The overall genotoxicity profile is negative for all three substances.

Uncertainty of the prediction:Orivone, p-tert butyl-trans-cyclohexanol and p-tert-butyl cyclohexyl acetate (mixture of trans and cos) are similar in molecular structure, toxico-kinetics and reactivity. It is likely that Orivone will mainly become a trans-alcohol instead of cis. At high doses ca >= 600 mg/kg bw significant clinical signs and body weight decrease can be expected. This may have led to mortality as is seen in one / 25 females during pregnancy.

The NOAEL in the 90-day study is 240 mg/kg bw, because at this dose no clinical signs, body weight effects or other effects are seen that are considered adverse. In view of the dose selection the NOAEL in the 90-day study is 240 mg/kg bw and in the developmental toxicity study 160 mg/kg bw. The NOAEL of the developmental toxicity study will conservatively be used as a NOAEL for a sub-chronic exposure because at this dose also no effects were seen in the 90-day study. This NOAEL of 160 mg/kg bw is converted to a NOAEL for Orivone resulting in an overall NOAEL for systemic toxicity of 136 mg/kg bw (160 mg/kg bw of the acetate / 198 MW of the acetate*168 MW of Orivone).

5. Data matrix

The relevant information on physico-chemical properties and toxicological characteristics are presented in the data Matrix.

6. Conclusions per endpoint for hazard, C&L and dose descriptor

For p-tert butyl-trans-cyclohexanol a well conducted 90-day repeated dose toxicity test with a 28 days recovery element is available (OECD TG 408, GLP and Rel 1) with a NOAEL of 240 mg/kg bw (LOAEL 800 mg/kg bw). In a developmental toxicity similar effects are seen at the high dose (640 mg/kg bw) and with a NOAEL of 160 mg/kg bw. The NOAEL of the developmental toxicity study will conservatively be used as a NOAEL for a sub-chronic exposure because at this dose also no effects were seen in the 90-day study. This NOAEL of 160 mg/kg bw is converted to a NOAEL for Orivone resulting in an overall NOAEL for systemic toxicity of 136 mg/kg bw (160 mg/kg bw of the acetate / 198 MW of the acetate*168 MW of Orivone).

Final conclusion on hazard, C&L, DNEL and risk characterization

Orivone has a NOAEL of 136 mg/kg bw/day for sub-chronic repeated toxicity which will be forwarded to the risk assessment

Data matrix for assessment of repeated dose toxicity of Orivone using read-across from p-tert-butyl-trans-cyclohexanol and p-tert-butyl cyclohexyl acetate.

Source/target	Target	Source	Source
Common names	Orivone	p-tert butyl-trans-cyclohexanol	p-tert-butyl cyclohexyl acetate (multi constituent)
Chemical structures
CAS No.	16587-71-6	21862-63-5	32210-23-4 (generic)
EINECS	240-642-0	700-127-8	250-954-9
Tanimoto	1	0.77	0.63
Empirical formula	C11H20O	C10H20O	C12H22O2
Molecular weight	168.28	156.267	198.3
Physical state	Liquid	Solid	Liquid
Melting point °C	< -20 (IFF measured)	78 (ECHA dissemination site)	< -50 (ECHA dissemination site, Kl4)
Boiling point °C	246.8 (IFF measured)	208.2 - 214.23(ECHA disseminated site)	243 (measured) (ECHA dissemination site)
Vapour pressure Pa	4.2 at 24°C (IFF measured )	0.74 at 20°C (measured) (ECHA dissemination site)	≤7.9 at 25°C (measured)  (ECHA dissemination site)
Water solubility mg/L	370.8 at °C(IFF measured)	132.2 at 20°C (ECHA dissemination site)	< 39.6 mg/L at 20 °C (measured) 3.55 mg/L at 25°C (QSAR estimation) (ECHA dissemination site)
Log Kow	3.9 at 25°C (IFF measured)	3.42 (ECHA disseminated site)	4.8 at 25°C (ECHA dissemination site)
Human health
Acute oral tox mg/kg bw	LD50-rat = 4700 (OECD TG 401)	LD50 – rat > 2000 (OECD TG 401 ECHA dissemination site)	LD50 – rat ca. 3370 (OECD TG 401 ECHA dissemination site)
Acute dermal tox mg/kg bw	LD50 rabbit = 4700	No data available	LD50 > 4680 (ECHA dissemination site)
Repeated dose toxicity (OECD TG 408)	136 Read-across from p-tert butyl-trans-cyclohexanol and p-tert-butyl cyclohexyl acetate	NOAEL 240 mg/kg bw (OECDTG 408)	No data available
Maternal toxicity in the Developmental toxicity test (OECD TG 414)	136 mg/kg bw using Read-across from p-tert-butyl cyclohexyl acetate (multi constituent) after conversion.	No data available	NOAEL maternal 160 mg/kg bw/day

 

References

Cheo 1967: Cheo, K.L., Elliott, T.H., and Tao, R.C.C., The metabolism of isomeric tert-butyl cyclohexanones, Brioche. J., 104, 198-204. 1967

Justification for classification or non-classification

For Orivone the NOAEL is set at 136 mg/kg bw for sub-chronic exposure. At >= 600 mg/kg bw significant effects are seen e.g. decreased body weight. Based on this Orivone does not need to be classified for repeated dose toxicity according to EU CLP (EC 1272/2008 and its amendments).