3,4-dihydroxy-1-[(Z)-octadec-9-enyl]pyrrolidine-2,5-dione

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics

Type of information:

other: Expert Statement

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Statement is based on valid study data.

Data source

Reference

Reference Type:

other:

Title:

Unnamed

Year:

2011

Report date:

2011

Materials and methods

Objective of study:

toxicokinetics

Principles of method if other than guideline:

The physicochemical properties of the test substance, and extensive toxicity studies in animals provide strong support in determining the ADME profile for this substance, and therefore may substitute for the experimentation of in vivo effects.

GLP compliance:

no

Test material

Test material information

Constituent 1

Radiolabelling:

no

Results and discussion

Main ADME results

Main ADME results 1

Type:

absorption

Results:

Via GI-Tract and skin is possible; inhalation exposure is irrelevant and absorption is not applicable.

Main ADME results 2

Type:

distribution

Results:

Via blood to target organs of toxicity

Main ADME results 3

Type:

metabolism

Results:

Metabolic changes assumed

Main ADME results 4

Type:

excretion

Results:

Elimination via urine or feces were supposed to be relevant

Metabolite characterisation studies

Metabolites identified:

yes

Details on metabolites:

Three representative chemical structures were selected to show function groups that are assumed to be candidate substrates for various enzymatic reactions. QSAR approach was used to predict the metabolism and kinetic profiles (OECD ToolBox version 1.1).

GI Metabolism Simulator predicted 0 metabolites.

Liver Metabolism Simulator predicted 7 metabolites at function groups indicated by black arrows (since this a symmetric structure, only one side chain was used for demonstration purpose. The same predictions on reaction patterns were applicable for the other 3).
-CH3: Hydroxylation of aliphatic carbon mediated by P450, followed by oxidations of alcohols to aldehydes and carboxylic acids by alcohol dehydrogenase and aldehyde dehydrogenase.
-CH2: Hydroxylation of aliphatic carbon mediated by P450, followed by oxidations of alcohols to aldehydes and ketone.

Microbial Metabolism Simulator predicted 16 metabolites. Function groups were indicated by red arrows, and conversion to different metabolites was presented in a numeric order.
- S -> Zn: oxidative desulfuration (-O -> Zn);
-Zn-S-: reduction (-Zn-SH)
-P-O-: hydrolysis mediated by esterase; and the freed alcohol undergo series oxidation.

Any other information on results incl. tables

Adsorption

 

Physico-chemical properties and the results of acute and repeat dose toxicity studies with animals for this substance are available to determine a toxicokinetic profile. The substance has a low molecular weight (381.2 gram MW; < 500 Mn Dalton), low water solubility (≤ 1.3 × 10-4 g/L at 20oC), and a high log Pow of 4.54 - 7.81 (6.84 major peak). These properties indicate that dermal absorption will be limited. This prediction is consistent with the absence of systemic toxicity following acute dermal exposure to rabbits. Although this substance has low water solubility, some oral absorption is expected via micellular solubilization due to its relatively high estimated log Pow (> 4). The results of the acute and repeat dose oral studies with rats indicate that significant oral absorption is limited to high, repeat dose exposures. While the low vapor pressure (1.6x10^-6kPa @ 25° C) greatly limits the potential for absorption, some absorption may occur via micellular solubilization of vapors and following the inhalation of mists or aerosols. The normal clearance mechanisms of the lung may further limit the absorption of this substance.

 

Distribution

 

Once this substance is absorbed, it will be distributed via the blood to the liver and other tissues. Due to its lipophilic nature it is expected to be readily absorbed by cells of the organs and tissues that it contacts. The oral combined repeat dose toxicity/reproduction/development study provides evidence that this substance can be distributed and adsorbed by various tissues. The high total protein in high dose males during the exposure and recovery phases, and to a lesser extent in the females, indicates that the substance has been absorbed by and may be causing effects on the liver or kidneys, which appear to be non-adverse due to the absence pathological changes. Males treated at the high dose also showed effects on the bone marrow and thymus providing evidence of further distribution.

 

Metabolism

 

The structure of the substance provides information that helps predicts the probable metabolic pathways. Glucuronidation of the alcohol moiety is likely to occur via the action of glucuronosyltransferases that are present in many tissues. The side chain also may be subject to oxidative metabolic reactions such as aliphatic hydroxylation, alkene epoxidation, and/or N-dealkylation of the side chain to form an aldehyde. The OECD Toolbox liver, skin, and microbial metabolism simulators also predict that this substance will be readily metabolized to more soluble substances. In addition to conjugation reactions with phase II enzymes, the QSAR tool also predicts that hydroxylation, reduction, and oxidative metabolism of this substance will occur.

 

Elimination

 

The primary route of eliminated is expected to be the urine and bile. The more soluble metabolites are expected to be readily eliminated. Because this substance has a low water solubility, very little is expected to be eliminated unchanged.

 

Conclusion

 

The physical-chemical properties and toxicological findings from animal studies provide a valid basis for determining the ADME profile for this substance. These data indicate that the low water solubility and high log Kow limit absorption. However, when it is absorbed it is distributed via the blood to the liver and other tissues. An assessment of the structure and the use of the OECD OSAR toolbox indicates that this substance will be readily metabolized with the soluble metabolites being readily eliminated in the urine and bile.

 

 

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): other: Bioaccumulation in exposed organisms is predicted to be unlikely.
The toxicokinetic profile of the test substance was not determined by actual absorption, distribution, metabolism or excretion measurements. Rather, the physical chemical properties of this substance were integrated with data from acute and repeated-dose toxicity studies to create a prediction of toxicokinetic behavior. And it is concluded that: Absorption in GI-Tract is relevant, dermal absorption is very low, and inhalation irrelevant
Distribution via blood to target organs of toxicity
Metabolic changes assumed
Elimination is assumed, bioaccumulation supposed to be irrelevant.