The metabolism of 3,7-dimethyl-2,6-octadienal (citral) in rat hepatic mitochondrial and cytosolic fractions. Interactions with aldehyde and alcohol dehydrogenases.
Citral (3,7-dimethyl-2,6-octadienal), a flavoring and fragrance agent, is associated with a variety of biochemical and toxicological effects. Reports of the in vivo metabolism of citral suggest that a primary route of metabolism is conversion to the corresponding acid species presumably by aldehyde dehydrogenases (ALDH). In the present study, hepatic mitochondrial and cytosolic fractions were prepared from male Sprague-Dawley rats to assess in vitro metabolism of citral. Evidence of ALDH-mediated citral oxidation was not seen in either subcellular fraction. On the contrary, citral was found to be a potent inhibitor of acetaldehyde oxidation by the low-KM mitochondrial form of ALDH. Measurement of the in vitro acetaldehyde oxidation rates of this isozyme in the presence of citral lead to the estimation of a Ki of 360 nM. Further studies of citral effects on low-KM mitochondrial ALDH indicate that inhibition is by a linear mixed-type mechanism and does not involve citral binding at the NAD+ binding site. In addition, it was observed that citral was readily reduced to the corresponding alcohol by alcohol dehydrogenase ( ADH) in the cytosolic fraction. The reduction of citral in the presence of NADH proceeded at two distinct rates; an initial "fast" rate followed by a "slow" rate. Individual kinetic constants were calculated for the two rates. It is possible that the differential ADH-mediated reduction rates of citral are the result of varying affinities for the enzyme of the two citral isomers, geranial (trans) and neral (cis).(ABSTRACT TRUNCATED AT 250 WORDS)[1]References
- The metabolism of 3,7-dimethyl-2,6-octadienal (citral) in rat hepatic mitochondrial and cytosolic fractions. Interactions with aldehyde and alcohol dehydrogenases. Boyer, C.S., Petersen, D.R. Drug Metab. Dispos. (1991) [Pubmed]
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