Structure-based design and synthesis of new 4-methylcoumarin-based lignans as pro-inflammatory cytokines (TNF-α, IL-6 and IL-1β) inhibitors

Abstract Suppression of pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) along with nitric oxide reduction in RAW 264.7 cells by 7,8-dihydroxy-4-methylcoumarin, ethyl p -coumarate, ethyl caffeate and ethyl ferulate drove us to search structural-analogues of the aforementioned compounds through structure-based drug design. Docking studies revealed that substituted cinnamic acids and their ethyl esters ( 2-7c ) showed higher GoldScore-fitness (GSF) and non-bonding interactions with target proteins than 7,8-dihydroxy-4-methylcoumarin ( 1a ) and 7,8-dihydroxy-5-methylcoumarin ( 1b ). With this background, the methylcoumarins ( 1a and 1b ) and the cinnamic acid derivatives ( 2 - 7c ) were fused in different permutations and combinations to generate sixty novel fused-cyclic coumarinolignans (FCLs) ( 8 – 13k ). Docking studies on 8 – 13k indicated that several FCLs possess higher GSF, interesting active site interactions and distinctive π-π interactions compared to the standards (cleomiscosin A, diclofenac Na and prednisolone). Based on these findings, four novel FCLs ( 9d , 10d , 11d and 11e ) were synthesized and tested for inhibition effect on TNF-α, IL-1β and IL-6 expressions in LPS and oxalate crystal-induced in-vitro models. Compound 10d exhibited significant effect ( P 50 value of 8.5 μM against TNF-α. Compound 11e possessed IC 50 values of 13.29 μM and 17.94 μM against IL-6 and IL-1β, respectively. Study on SAR corroborated the requirement of C-4-methyl substituent in the coumarin moiety, dihydroxyl groups in the phenyl ring, and esterification of lignans for potent activity. Additionally, the reported excellent anti-inflammatory activity of cleomiscosin-A-glucoside was corroborated by from the higher GSF and better hydrophobic interactions than cleomsicosin A in the docking study. As an outcome, some novel and potentially active FCLs acting through NFκB and caspase 1 signaling pathways have been discovered as multiple cytokine inhibitors.