Quantitative structure-activity relationship study of benzylsulfanyl imidazoles as cytokine release inhibitors

Abstract

Benzylsulfanyl imidazole derivatives (Figure ) have shown their ability to inhibit the release of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) from peripheral blood mononuclear cells or human whole blood. Such anticytokine actions of these congeners are quantitatively studied using Fujita-Ban and Hansch type analyses. The Fujita-Ban study resulted in the contributions of different substituents and the parent moiety for the inhibitions of cytokines TNF-α and IL-1β. The substituents that have a higher positive contribution to the given activity, relative to substituents of the parent moiety at different positions were then used to obtain a trend for the active analogues. None of the substituents present at X, Y, 2-R and 3-R, appears to be advantageous over the substituents of the parent moiety for inhibition of both the cytokines. However, the substituents at 4-R, 5-R and 6-R help to improve the inhibitory actions of the compounds for both cytokines. The optimal activities seem to be manifested by compounds in which 4-R, 5-R and 6-R are substituted respectively by OH (or SOCH₃ and SO₂CH₃), Cl and OH for inhibition of TNF-α, whereas by SOCH₃ (or SO₂CH₃ and OH), H and OH for inhibition of IL-1β. The Hansch type analysis, on the other hand, revealed that the F-substituents of the X-position and a less bulky structural moiety such as − S(CH₂)₂– at the Y-incision are advantageous in improving the inhibitory action towards TNF-α. Similarly, a less bulky/polar substituent present at 2-R and not having a hydrogen-bond donor property, while a more hydrophobic substituent at 3-R and hydrogen-bond acceptor substituent at 4-R are helpful in augmenting inhibitory activity of a compound. However, for inhibition of cytokine IL-1β, it emerged that the X-substituents that transmits a higher negative resonance effect, the Y-substituent that offers less molecular bulk are beneficial. The R-substituents, being more electron donors at the meta-position, less hydrophobic at the para-position and offering smaller refractivity (less bulky and or polar) at the ortho-position are likewise helpful in improving the activity of a compound.

Keywords::

• Benzylsulfanyl imidazole derivatives
• Cytokine inhibition activity
• QSAR analysis
• Fujita-Ban and Hansch approaches
• Physicochemical properties
• substituent selection in drug design

Acknowledgements

Authors are thankful to the Department and the College for providing the necessary facilities to complete this work.