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EC number: 248-096-5 | CAS number: 26896-48-0
Endpoint summary
Administrative data
Link to relevant study record(s)
Description of key information
Octahydro-4,7-methano-1H-indenedimethanol (TCD Alcohol DM) will primarily be metabolized at the hydroxymethyl substituents forming the respective aldehydes and subsequently acids. Information on the metabolic fate of the alicyclic tricyclodecane moiety is not available.
Key value for chemical safety assessment
Additional information
For octahydro-4,7-methano-1H-indenedimethanol (TCD Alcohol DM), information on toxicokinetics is very limited. No studies with mammalian test systems could be located.
The only substance specific information originates from a test on biodegradation (NITE, 2004; MITI I test). In this study two metabolites were characterised. In the bacterial test suspension, partial oxidation resulted in the formation of 2 - 7% of an aldehyde (oxidation of one of the hydroxymethyl groups) and of 12 - 15% of a carboxylic acid (further oxidation of the formyl group). For the remainder of the test substance, there is no information on its fate. The results indicate that bacterial metabolism follows the same principle metabolic pathways as is typically found in mammalian systems.
TCD Alcohol DM consists of a tricyclic carbon frame with two methylol groups (hydroxymethyl substituents) connected to the frame at two distinct sites. These hydroxymethyl substituents constitute primary alcohols which can react following pathways typical for alcohols as chemical class of substances.
Metabolism of alcohols
Oxidation by Alcohol-dehydrogenase (ADH) and Aldehyde-dehydrogenase (ALDH)
It has been demonstrated in several studies using a variety of alcohols, that alcohols in general are oxidized rapidly to their corresponding aldehydes by alcohol dehydrogenases. The rate of oxidation increases with increase in chain length and with the presence of a double bond. The subsequent oxidation of the aldehydes to the corresponding acid is catalysed by dehydrogenase and oxidase enzymes. Most active is a NAD+/NADH-dependent aldehyde dehydrogenase present in the cytosol, the activity of which increases with increasing relative molecular mass of the aldehyde substrate. Endpoint of this oxidation process is the corresponding carboxylic acid. Aliphatic saturated carboxylic acids are metabolised by ß-oxidation via the fatty acid pathway or the tricarboxylic acid pathway, and finally degraded and metabolised completely.
Oxidation alternative pathways
If affinity to ADH is low or the carbon frame of the alcohol is voluminous, other pathways may become important. Oxidation at the carbon frame and formation of hydroxyl groups bound to the carbon frame may occur catalysed by microsomal cytochrome P-450 isoenzymes.
Conjugation (Phase II-reactions)
To increase solubility and to facilitate excretion, unpolar metabolites or unchanged xenobiotics are conjugated with polar endogenous substances. Prerequisite is the presence of a functional group such as an alcohol or carboxylic acid group in the molecule. Conjugates can be formed with glucuronide, sufate, acetate, amino acids, and glutathione. The newly formed products will have higher water solubility than the parent compounds and may be excreted via urine or bile. Alcohols as well as carboxylic acids are functional groups suitable for conjugation.
With bacterial suspensions it has been demonstrated that TCD alcohol DM undergoes oxidation of the alcohol group to aldehyde and carboxylic acid.
This pathway is expected also to happen in mammalian systems. But it cannot be estimated if only one hydroxyl group is oxidised or both and to what extent oxidation will proceed. In addition, further degradation of the carboxylic acid as with acyclic linear primary alcohols via the fatty acid pathway is impeded or not possible due to the tricyclic structure of the carbon frame. In principle, additional metabolic transformations are possible. Oxidation of the frame and conjugation are supplemental alternatives and can occur. Compared to simple acyclic linear primary alcohols, the metabolism of TCD Alcohol DM is expected to be more complex. In addition to aldehyde and carboxylic acid, other metabolites are likely to be formed. But due to lack of information, the metabolic fate of TCD Alcohol DM and the variety of metabolites formed in vivo cannot be estimated satisfactorily.
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