Cytochrome P450 4A11 inhibition assays based on characterization of lauric acid metabolites.

This study was designed to characterize lauric acid metabolism to facilitate the establishment of cytochrome P450 4A11 (CYP4A11) inhibition assay. Three metabolites (2-, 11-, and 12-hydroxylauric acids) were identified in pooled human liver microsomes based on comparisons with authentic standards. Reaction phenotyping using 14 recombinant CYPs showed that ω-hydroxylation was mediated dominantly by CYP4A11 and marginally by CYP4F3B. CYP2B6 played an exclusive role in the formation of 2-hydroxylauric acid. The production of 11-hydroxylauric acid was mediated by CYP2E1, CYP2C9, CYP2B6, CYP1A2, CYP3A4, and CYP4A11. The IC50 values of HET0016, a well-known pan-CYP4 inhibitor, against the formation of 12-, 11-, and 2-hydroxylauric acid were 1.0, 1.0, and 0.009 μM, respectively. Among the 50 natural compounds examined, plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone) inhibited the formation of 12-, 11-, and 2-hydroxylauric acid with IC50 values of 1.7, 2.3, and 2.7 μM, respectively. In the selectivity study, HET0016 inhibited CYP2B6 with an IC50 of 9.2 nM, as well as CYP1A2, CYP2C19, and CYP2E1 with IC50 values of 1-2 μM. Plumbagin inhibited all CYP enzymes tested with IC50 values of 1.7-3.0 μM. These methods can be used as tools to develop CYP4A11 inhibitors; simultaneous determination of the hydroxylauric acid metabolites provides further information on selectivity.