A series of novel diaryl substituted pyrazolyl 2,4-thiazolidinediones were synthesized via reaction of appropriate pyrazolecarboxaldehydes with 2,4-thiazolidinedione (TZD) and nitrobenzyl substituted 2,4-thiazolidinedione. The resulting compounds were screened in vitro for pancreatic lipase (PL) inhibitory activity. Two assay protocols were performed viz., methods A and B using p-nitrophenyl butyrate and tributyrin as substrates, respectively. Compound 11e exhibited potent PL inhibitory activity (IC50=4.81µM and Xi50=10.01, respectively in method A and B), comparable to that of the standard drug, orlistat (IC50=0.99µM and Xi50=3.72). Presence of nitrobenzyl group at N-3 position of TZD and nature of substituent at para position of phenyl ring at C-3 position of pyrazole ring notably affected the PL inhibitory activity of the tested compounds. Enzyme inhibition kinetics of 11e revealed its reversible competitive inhibition, similar to that of orlistat. Molecular docking studies validated the rationale of pharmacophoric design and are in accordance to the in vitro results. Compound 11e exhibited a potential MolDock score of -153.349kcal/mol. Further, the diaryl pyrazolyl wing exhibited hydrophobic interactions with the amino acids of the hydrophobic lid domain. Moreover, the carbonyl group at 2nd position of the TZD ring existed adjacent to Ser 152 (≈3Å) similar to that of orlistat. A 10ns molecular dynamics simulation of 11e-PL complex revealed a stable binding conformation of 11e in the active site of PL (Maximum RMSD≈3Å). The present study identified novel thiazolidinedione based leads with promising PL inhibitory activity. Further development of the leads might result in potent PL inhibitors.
Keywords: Knoevenagel; Molecular modelling; Obesity; Orlistat; Pancreatic lipase; Pyrazole; Thiazolidinedione; pH indicator.
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