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Cinnamaldehyde Analogs as CYP2A6 Inhibitors: A Structure‐Activity Study
Author(s) -
Black Stephen,
Joseph Paul,
Higa Allyson,
Moyeen Ghina,
Ebisuya Kara,
Davis Madison,
Chan Jeannine,
Harrelson John
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.934.6
Subject(s) - cinnamaldehyde , chemistry , stereochemistry , cyp2a6 , potency , binding site , coumarin , cytochrome p450 , enzyme , biochemistry , organic chemistry , in vitro , cyp3a4 , catalysis
Previously we observed that trans ‐cinnamaldehyde is a metabolism‐dependent inhibitor of cytochrome P450 2A6 (CYP2A6). The aim of this study was to investigate the structural basis for the binding affinity and inhibition potency of trans ‐cinnamaldehyde structural analogs, with the ultimate goal of identifying more potent and selective inhibitors as potential smoking cessation agents. For this study, we used Autodock Vina to model binding orientations of a series of analogs, with substitutions on the aromatic ring and the alpha/beta positions of trans ‐cinnamaldehyde, and to estimate binding affinity (K D values). Binding affinity was measured using a spectrophotometric ligand binding titration, and inhibition (IC 50 values) was evaluated by measuring coumarin hydroxylase activity using a 96‐well plate fluorescence assay. Autodock Vina best predicted the affinity of analogs with substitutions at the alpha and ortho positions. For example, the measured and predicted K D values for α‐bromo (8.2 ± 1.1 μM; 2.6 to 46.8 μM), α‐methyl (13.7 ± 0.6 μM; 1.9 to 8.6 μM), and α‐chloro (9.6 ± 1.2 μM; 3.1 to 23.8 μM) substitutions were in reasonable agreement. IC 50 values were also consistent with the measured and predicted K D values: 3.7 ± 0.6μM (α‐bromo), 5.3 ± 0.8 μM (α‐methyl), and 4.2 ± 0.7 μM (α‐chloro). The modeling predicted the 2,6‐difluoro analog (K D = 4.3 ± 0.3 μM) would have modestly greater affinity for CYP2A6 than trans ‐cinnamaldehyde (9.6 ± 0.4 μM), and this was reflected in the inhibition data where the IC 50 values for the difluoro analog and trans ‐cinnamaldehyde were 4.8 ± 1.2 μM and 6.0 ± 1.2 μM, respectively. In the case of trans ‐cinnamaldehyde, the predicted K D (9.6 ± 0.4 μM) was also consistent with the measured spectral binding constant (14.9 ± 6.3 μM). The inhibition data shows that the alpha and ortho substitutions were more potent inhibitors than the meta‐ and para‐ substituted analogs; Autodock Vina predictions were consistent with this. For the alpha substitutions, larger groups (amyl‐and hexyl‐) were not as potent inhibitors as smaller ones (bromine, chlorine, methyl). The smaller groups were approximately equally effective at inhibiting 2A6 as trans ‐cinnamaldehyde itself. Support or Funding Information Medical Research Foundation of Oregon, M.J. Murdock Charitable Trust 1Molecular modeling of trans ‐cinnamaldehyde inside the active site of CYP2A6. Trans ‐Cinnamaldehyde has been colored yellow. The heme group of CYP2A6 has been colored orange. Residues are colored green and white. Oxygens and Nitrogens are colored red and blue, respectively.