Adipic acid, compound with hexane-1,6-diamine (1:1)

Endpoint summary

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

basic toxicokinetics in vivo

Type of information:

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

Adequacy of study:

key study

Study period:

no data

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:

In Vivo Studies: Different doses of DEHA were administered by gavage to Wistar male rats for 5 days. Urine was collected each morning and metabolites were extracted.
In Vitro Studies: Hepatocytes were isolated by a two step in situ perfusion technique. The test substance dissolved in dimethyl formamide was added to the cultivated monolayers 24 h after seeding and added at each 24 h medium change. Medium metabolites were extracted.
Methods of Analysis of Biological Extracts: Glucuronides as their methyl and trimethylsilyl derivatives were identified by gas chromatography/mass spectrometry.

GLP compliance:

not specified

Species:

rat

Strain:

Wistar

Sex:

male

Details on test animals or test system and environmental conditions:

no data

Route of administration:

oral: gavage

Vehicle:

corn oil

Duration and frequency of treatment / exposure:

single dose

Dose / conc.:

665 mg/kg bw (total dose)

Dose / conc.:

1 500 mg/kg bw (total dose)

Details on dosing and sampling:

Different doses of DEHA were administered by gavage to Wistar male rats for 5 days. Control animals received the vehicle alone (0.5 ml corn oil). Urine was collected each morning and extracted.

Details on excretion:

After 24 h, no DEHA is recovered in rat urine.

Metabolites identified:

yes

Details on metabolites:

Adipic acid is the main metabolite of DEHA. Only the EH metabolic pathway shows further metabolites, mainly EHA, which is either conjugated or submitted to omega and omega-1 pathways, giving respectively 2-ethyl hexanedioic acid and 2-ethyl-5-hydroxyhexanoic acid. The identification of all metabolites was in agreement with those in previous EH metabolism study. According to the authors, it appears that EHA glucuronidation is dose and time dependent but that EH glucuronidation is more stable.
See also attached file.

Executive summary:

After oral administration of 665 or 1500 mg di(2-ethylhexyl) adipate/kg  bw to male rats up to 95 % of the theoretical amount from Di(2 -ethylhexyl)adipate (DEHA) was found  as adipic acid in urine on day 1 after dosing. The urinary recovery was  about 50%. Carbon dioxide (CO2) exhalation was not studied. Other metabolites were oxidized and conjugated forms of 2-ethyl hexanoic acid.

Reference 2

Endpoint:

basic toxicokinetics in vivo

Type of information:

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

Adequacy of study:

key study

Study period:

no data

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:

Study to quantitatively estimate the adipic acid and its metabolic products in tissues and urine.

GLP compliance:

no

Remarks:

pre-GLP study

Radiolabelling:

yes

Remarks:

14C

Species:

rat

Strain:

not specified

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
male albino rats
- Source: Carworth Farms
- Weight at study initiation: 150 - 250 g
- Fasting period before study: yes, ca. 24 h prior to dose
- Individual metabolism cages: yes

ENVIRONMENTAL CONDITIONS: no data

No further data

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
A solution containing approximately 50 mg radioactive adipic acid in 2-4 ml of water was administered. No further data.

Duration and frequency of treatment / exposure:

single dose

Dose / conc.:

50 other: mg/rat

Remarks:

equivalent to ca. 7.5 - 12.5 mg/kg bw, depending on the individual body weight

No. of animals per sex per dose / concentration:

no data

Control animals:

no

Details on distribution in tissues:

The tissues from the sacrificed rats showed very little residual radioactivity. Of all the tissues examined, the highest activity appeared in
the liver and kidney.

Details on excretion:

Six radioactive metabolites including adipic acid were found in the urine. Urea and glutamic, lactic, adipic, ß-ketoadipic, and citric acids
were identified as metabolites of adipic acid in the urine.
Up to 70% of the radioactivity accumulates in the breath during the 24-hour experimental period. Approximately 70% of the dose was exhaled as carbon dioxide within 6 hours after administration.

Metabolites identified:

yes

Details on metabolites:

Urea and glutamic, lactic, adipic, ß-ketoadipic, and citric acids were identified as metabolites of adipic acid (for details see "Remarks on results including tables and figures").
The presence of ß-ketoadipic acid pointed to ß-oxidation of adipic acid during its metabolism. Accordingly, the formation of succinic acid and acetic acids in vivo from adipic acid was observed.

The distribution of radioactivity in the urinary fractions is presented in the attached file. The following substances were identified tentatively from the peaks of the chromatogram:

• peak 1: urea (identified by melting point)
• peak 2: glutamic acid (positive to ninhydrin test)
• peak 3: this peak has not yet been identified
• peak 4: lactic and beta-keto acids (positive for chemical test on lactic acid. Beta-ketoadipic acid was identified by the ultraviolet spectrum of its phenylhydrazone. The unknown and pure beta-ketoadipic phenylhydrazones gave identical absorption bands at 292 nm. Furthermore, the phenylhydrazone was radioactive and represented 50% of the radioactivity)
• peak 5: adipic acid (identified by paper chromatography)
• peak 6: the identity of this peak has not been established
• peak 7: citric acid (identified by specific test)

Executive summary:

Adipic acid is absorbed and metabolised by normal metabolic processes in the rat. When 50 mg 14C-labelled adipic acid was administered by gavage to fasted rats, metabolic products found in the urine overnight were identified as urea, glutamic acid, beta-ketoadipic acid. Unchanged adipic acid was also detected in the urine. Seventy percent of the dose was exhaled as carbon dioxide within 6 hours after administration. The tissues showed very little radioactivity.

Reference 3

Endpoint:

basic toxicokinetics in vitro / ex vivo

Type of information:

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

Adequacy of study:

key study

Study period:

no data

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:

Based on analysis by gas chromatography-mass spectrometry, metabolites of 1,6-diaminohexane obtained in the liver of rat males were identified.

GLP compliance:

not specified

Radiolabelling:

no

Metabolites identified:

yes

Details on metabolites:

1,6 -Diaminohexane was converted by diamine oxidases (DAO) into 3,4,5,6-tetrahydro-2H-azepine which was further metabolized by aldehyde oxidase (AO) to caprolactam and 6 -aminohexanoic acid. See figure in attached file.

1,6 -Diaminohexane is a metabolite of hexamethylene bisacetamide (HMBA).

Executive summary:

1,6-diaminohexane is metabolized in vitro by diamine oxidase to 3,4,5,6 -tetrahydro-2H-azepine and this metabolized further by aldehyde dehydrogenase to 6-aminohexanoic acid and caprolactam in the rat liver.

The metabolic fate of 1,6-diaminohexane is similar to that of putrescine and cadaverine in that a cyclic imine is an intermediate in the formation of metabolites with ring (lactam) and chain (amino acid) structures.

Reference 4

Endpoint:

basic toxicokinetics in vivo

Type of information:

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

Adequacy of study:

key study

Study period:

no data

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Objective of study:

distribution

Principles of method if other than guideline:

The distribution of radiocarbon following i.v. injection of 1,6-Hexamethylenediamine-1 ,6-[14C]dihydrochloride ([14C]HMDA) was investigated using whole-body autoradiography. Male and female rats were administered [14C]HMDA, and one animal of each sex was killed at 1 h and at 24 h post-injection. Rats were administered [14C]HMDA) by gavage. Excreta, including expired air, were collected for 72 h. Different tissues were excised and analyzed for residual radioactivity.

GLP compliance:

not specified

Radiolabelling:

yes

Remarks:

14C

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
male and female F-344 rats (CDF(F-344)/CrIBR) rats
- Source: Charles River, Kingston, NY
- Weight at study initiation: 200 - 250 g
- Housing: in hanging wire cages
- Diet (ad libitum): NIH-07 rodent diet (Zeigler Bros., Gardners, PA)
- Water (ad libitum): tap water
Serum from all experimental rats was found free of antibody titers to the normal screen of rat viruses.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): ca. 20 - 22°C (original value: 70 +/- 2 °F)
- Humidity (%): 50 %
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

other: oral: gavage or intravenous

Vehicle:

physiological saline

Duration and frequency of treatment / exposure:

single dose

Dose / conc.:

0.4 mg/kg bw (total dose)

Remarks:

HDMA (corresponding to 25 µCi of [14C]HMDA-2 HCI/250 g body weight)

No. of animals per sex per dose / concentration:

4 males (oral dosing);
unstated number of males and females (intravenous dosing)

Control animals:

no

Positive control reference chemical:

no

Details on distribution in tissues:

Tissue distribution (injection study)
Several tissues were examined for the presence of residual radioactivity 72 h after oral administration of HMDA (see attached file). Of these tissues, the prostate contained the highest concentration of radioactivity.
Whole-body autoradiography provided further information concerning the tissue distribution of HMDA. 1 h after injection, the intestine contained the greatest amount of radioactivity in a male rat. The autoradiographs showed that the label was concentrated in the mucosal lining of the intestine. The liver and kidney closely followed the intestine in intensity of radioactivity. The prostate gland was well below the liver in intensity of radiolabel, but above the intensity of the blood. There was little radioactivity in the brain or testes.
At 24 h post-injection, the prostate gland contained the greatest concentration of radioactivity. The intestine and liver appeared to follow the prostate in the amount of radiolabel they contained. Thus, [14C]-HMDA either accumulates slowly in the prostate or persists in that gland for a relatively long time.
The uterus of the female rat was found to have a high concentration of radiolabel 1 h after injection but not 24 h afterwards. The accumulation of radiolabel in the uterus may be dependent on the estrous cycle and the stage during which the compound is administered. Little radioactivity was found in the ovary at either time period.

Details on excretion:

Disposition of [14C]HMDA (oral study)
The principal route of elimination of radioactivity following oral administration was the urine (47% of the dose). Approx. 20% of the administered radioactivity was excreted as CO2 over a 72-h period while the feces contained 27%. Very little radioactivity was retained by the animals 72 h after treatment (< 1.5%). Urine samples from treated animals were analyzed by HPLC and TLC and were observed to contain two major peaks of radioactivity. One of these, comprising 30% of the total radioactivity in the urine, comigrated with authentic HMDA in both chromatographic systems.

Executive summary:

Following oral administration of 1,6-[14C]diaminohexane (hexamethylenediamine, HMDA) to male Fischer-344 rats, approximately 20% of the administered dose was recovered as 14CO2 after 72 h. Urinary and fecal excretion accounted for 47% and 27% of the administered radioactivity, respectively. Of several tissues examined, the highest concentrations of residual radioactivity were found in the prostate at 24 and 72 h post-administration.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

AH salt is a mixture of adipic acid and 1,6-hexanediamine (1:1). No studies are available for AH salt, therefore studies of the two single compounds or of di-2 -(ethylhexyl)adipate (which is metabolically converted to adipic acid) are used.

Adipic acid (CAS 124 -09 -4)

Adipic acid is absorbed and metabolised by normal metabolic processes in the rat. When 50 mg 14C-labelled adipic acid was administered by gavage to fasted rats, metabolic products found in the urine overnight, were identified as urea, glutamic acid, and beta-ketoadipic acid. Unchanged adipic acid was also detected in the urine. Seventy percent of the dose was exhaled as carbon dioxide within 6 hours after administration. The tissues showed little radioactivity. (Rusoff et al, 1960)

1,6-Hexamethylenediamine-1,6-[14C]dihydrochloride (CAS 6055 -52 -3)

Following oral administration of 1,6-Hexamethylenediamine-1,6-[14C]dihydrochloride (hexamethylenediamine, HMDA) to male Fischer 344 rats, approximately 20% of the applied dose was recovered as 14CO2 after 72 hours. Urinary and fecal excretion accounted for 47% and 27% of the administered dose, respectively. Of several tissues examined, the highest concentrations of residual radioactivity were found in the prostate at 24 and 72 hours post-administration. (David and Heck, 1983)

1,6 -Diaminohexane (CAS 124 -04 -9)

1,6 -Diaminohexane is metabolised in vitro by diamine oxidase to 3,4,5,6 -tetrahydro-2H-azepine and this is further metabolised by aldehyde dehydrogenase to 6 -aminohexanoic acid and caprolactam in the rat liver. The metabolic fate of 1,6 -diaminohexane is similar to that of putrescine and cadaverine in that a cyclic imine is an intermediate in the formation of metabolites with ring (lactam) and chain (amino acid) structures. (Subramanyam et al, 1989)

Di-2 -(ethylhexyl)adipate (DEHA) (CAS 103 -23 -1)

At 24 hours following administration, no DEHA was recovered in rat urine Adipic acid was the main metabolite of DEHA. Only the EH (ethylhexane) metabolic pathway showed further metabolites, mainly ethylhexanoic acid (EHA), which was either conjugated or submitted to omega- and omega-1 -pathways, yielding 2 -ethylhexanedioic acid and 2 -ethyl-5 -hydroxyhexanoic acid, respectively. The identification of all metabolites was in agreement with those in previous EH metabolism studies. According to the authors, it appeared that EHA glucuronidation was dose- and time-dependent, but that EH glucuronidation was more stable. (Cornu et. al, 1988)