In:
Drug Metabolism Letters, Bentham Science Publishers Ltd., Vol. 14, No. 1 ( 2021-05-05), p. 41-53
Abstract:
Carbon-carbon bond cleavage of a saturated aliphatic moiety is rarely seen in
xenobiotic metabolism. Olanexidine (Olanedine®), containing an n-octyl (C 8 ) side chain, was mainly
metabolized to various shortened side chain (C 4 to C 6 ) acid-containing metabolites in vivo in preclinical
species. In liver microsomes and S9, the major metabolites of olanexidine were from multi-oxidation on its n-octyl (C 8 ) side chain. However, the carbon-carbon bond cleavage mechanism of n-octyl (C 8 )
side chain, and enzyme(s) responsible for its metabolism in human remained unknown. Methods: A pair of regioisomers of α-ketol-containing C 8 side chain olanexidine analogs (3,2-ketol
olanexidine and 2,3-ketol olanexidine) were synthesized, followed by incubation in human liver microsomes, recombinant human cytochrome P450 enzymes or human hepatocytes, and subsequent metabolite
identification using LC/UV/MS. Results: Multiple shortened side chain (C 4 to C 6 ) metabolites were identified, including C 4 , C 5 and C 6 -
acid and C 6 -hydroxyl metabolites. Among 19 cytochrome P450 enzymes tested, CYP2D6, CYP3A4
and CYP3A5 were identified to catalyze carbon-carbon bond cleavage. Conclusions: 3,2-ketol olanexidine and 2,3-ketol olanexidine were confirmed as the key intermediates in
carbon-carbon bond cleavage. Its mechanism is proposed that a nucleophilic addition of iron-peroxo species, generated by CYP2D6 and CYP3A4/5, to the carbonyl group caused the carbon-carbon bond cleavage
between the adjacent hydroxyl and ketone groups. As results, 2,3-ketol olanexidine formed a C 6 side
chain acid metabolite. While, 3,2-ketol olanexidine formed a C 6 side chain aldehyde intermediate, which
was either oxidized to a C 6 side chain acid metabolite or reduced to a C 6 side chain hydroxyl metabolite.
Type of Medium:
Online Resource
ISSN:
1872-3128
DOI:
10.2174/1872312813666191125095818
Language:
English
Publisher:
Bentham Science Publishers Ltd.
Publication Date:
2021
SSG:
15,3
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