Synthesis, In Silico Studies, and In Vitro Anti-Inflammatory Activity of Novel Imidazole Derivatives Targeting p38 MAP Kinase

Abstract

A series of eight novel N-substituted [4-(trifluoro methyl)-1H-imidazole-1-yl] amide derivatives (AA1-AA8) were synthesized, characterized, and evaluated for their in vitro p38 MAP kinase anti-inflammatory inhibitory activity. The synthesized compounds were obtained by coupling [4-(trifluoromethyl)-1H-imidazole-1-yl] acetic acid with 2-amino-N-(Substituted)-3-phenylpropanamide derivatives utilizing 1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b] pyridinium 3-oxide hexafluorophosphate as a coupling agent. Various spectroscopic methods established and confirmed their structures, specifically, ¹H NMR, ¹³C NMR, Fourier transform infrared (FTIR), and mass spectrometry. In order to emphasize the binding site of the p38 MAP kinase protein and newly synthesized compounds, molecular docking studies were carried out. In the series, compound AA6 had the highest docking score of 7.83 kcal/mol. The ADME studies were performed using web software. Studies revealed that all the synthesized compounds were orally active and showed good gastrointestinal absorption within the acceptable range. Lipinski's "rule of five" was used to determine drug-likeness. The synthesized compounds were screened for their anti-inflammatory activity by performing an albumin denaturation assay in which five compounds (AA2, AA3, AA4, AA5, and AA6) were found to exhibit substantial activity. Hence, these were further selected and proceeded for the evaluation of p38 MAP kinase inhibitory activity. The compound AA6 possesses considerable p38 kinase inhibitory anti-inflammatory activity with an IC₅₀ value of 403.57 ± 6.35 nM compared to the prototype drug adezmapimod (SB203580) with an IC₅₀ value of 222.44 ± 5.98 nM. Some further structural modifications in compound AA6 could contribute to the development of new p38 MAP kinase inhibitors with an improved IC₅₀ value.

Figure 1

Imidazole-based p38 MAP kinase inhibitors.

Figure 2

Reaction scheme showing the synthetic pathway of the N-substituted [4-(trifluoro methyl)-1H-imidazole-1-yl] amide derivative (AA1–AA8).

Figure 3

Structure of final synthesized compounds N-substituted [4-(trifluoro methyl)-1H-imidazole-1-yl] amide derivative (AA1–AA8).

Figure 4

Position of protons (a–m).

Figure 5

IC₅₀ of Albumin denaturation inhibitory activity in μg/mL.

Figure 6

p38 MAP kinase activity (in percent, %) of selected compounds.

Figure 7

IC₅₀ of selected compounds as a function of p38 kinase inhibitory activity.

Figure 8

Docking pose and molecular interactions of SB203580 in the active site of p38 MAP kinase.

Figure 9

(a,c,e) Docking poses of the compounds AA8, AA6, and AA4 in the active site of p38 MAP kinase and (b,d,f) are the molecular interactions of the compounds AA8, AA6, and AA4 in the active site of p38 MAP kinase.

Figure 10

BOILED-Egg approach to predict gastrointestinal absorption and brain penetration of N-substituted [4-(trifluoro methyl)-1H-imidazole-1-yl] amide derivatives.