Undecanal

Endpoint summary

Description of key information

Undecanal is considered to be rapidly absorbed after oral and inhalation exposure. Rapid utilisation in the intermediary metabolism, and urinary excretion, but no bioaccumulation is expected to occur. 

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

No specific investigations on the toxicokinetics of n-undecanal are available, but there is sufficient general information because aldehydes are the primary metabolites of primary alcohols whose metabolism has been extensively investigated.

Aldehydes are rapidly absorbed following oral uptake and, according to UBA (2009), following inhalation exposure. Aldehydes are rapidly oxidised to their corresponding acids by aldehyde dehydrogenases. These enzymes are present in the cytosol at high levels, and also in mitochondria and in microsomes. According to Martini and Murray (1996), the activity of the enzyme increases with the molar masses of the substrates (values for undecanal: Km ~ 10 µM; Vmax ~ 25 nmol of NADH produced per minute and µg Protein; Martini and Murray, 1996). The resulting acids, i.e. undecanoic acid in the case of undecanal, may then enter different metabolic pathways. Undecanoic acid may be transported into mitochondria and undergo degradation in the fatty acid oxidation to acetyl-CoA and propionyl-CoA. The latter is converted to succinic acid via methylmalonyl-CoA. Acetyl CoA may be used for biosynthetic reaction, or can eventually enter the TCA cycle, which produces NADH₂  and FADH₂. NADH and FADH₂are subsequently used in the electron transport chain to produce ATP, the energy currency of the cell (JECFA, 1998; WHO, 1999).

Acids, e.g. undecanoic acid, may also be conjugated with glycine to form hippuric acids (O’Brien, 2005). Short chained acids may enter another pathway, i.e. reduction to the respective alcohols by cytosolic, NAD+-dependent alcohol dehydrogenases and conjugation with, e.g., glutathione (O’Brien, 2005), but this pathway is not considered to be relevant for undecanoic acid.

The main excretion pathway for remaining aldehyde metabolites is the urine (O’Brien, 2005; UBA, 2009).

To summarise, undecanal is expected to be predominantly oxidised to undecanoic acid. This is a linear, saturated fatty acid which is expected to be degraded and utilized via fatty acid oxidation and intermediary metabolism. It should, however, be noted that the aldehyde group may also cause reactions including covalent binding to nucleophils, especially locally at the point of entry, and at elevated concentrations.