Synthesis, molecular modelling, in vitro and in vivo evaluation of conophylline inspired novel benzyloxy substituted indole glyoxylamides as potent pancreatic lipase inhibitors

Abstract

Pancreatic lipase is a digestive enzyme involved in the hydrolysis of dietary fats. Orlistat, a potent pancreatic lipase inhibitor, is widely prescribed for long-term obesity treatment. Nevertheless, orlistat is reported for severe adverse effects including hepatotoxicity and pancreatitis. In the present study, a novel series of 11 benzyloxy substituted indole glyoxylamides were designed, synthesized and evaluated for in vitro pancreatic lipase inhibitory activity. Three analogues, 10b, 11b and 11c, exhibited potent activity (IC₅₀ ≤ 2.5 µM), with 11b exhibiting a potent IC₅₀ of 1.68 µM comparable to orlistat (IC₅₀ = 0.99 µM). Further, 11b exhibited reversible competitive inhibition with an inhibitory constant value of 0.98 μM. Molecular docking of these analogues was in agreement with in vitro results, wherein the MolDock scores exhibited significant correlation with their inhibitory activity (Pearson’s r = 0.7122). A 50 ns molecular dynamics simulation of 11b-pancreatic lipase complex confirmed the role of extended alkyl interactions along with π-π stacking and π-cation interactions, in stabilizing the ligand (Maximum RMSD ≈ 3 Å) in the active site. Gastro-intestinal absorption and toxicity prediction of the three potent analogues highlighted the suitability of 11b for in vivo experiments. 11b at a dose of 20 mg/kg exhibited anti-obesity efficacy comparable to orlistat (10 mg/kg), wherein the serum triglycerides were found to be 94.95 and 83.85 mg/dL, respectively. Further, faecal triglyceride quantification indicated 11b to act through pancreatic lipase inhibition similar to orlistat. The present study identified a novel pancreatic lipase inhibitory benzyloxy substituted bis(indolyl) glyoxylamide 11b, with promising anti-obesity activity.

Communicated by Ramaswamy H. Sarma

Keywords:

• Benzyloxy indole glyoxylamides
• conophylline
• geranyl
• inhibition kinetics
• molecular dynamics
• pancreatic lipase
• pre-clinical studies

Acknowledgements

The authors acknowledge Birla Institute of Technology and Science, Pilani (BITS Pilani), Pilani Campus, Pilani, Rajasthan, India for providing NMR and other necessary laboratory facilities. Dr. S. N. C. Sridhar acknowledges the Council for Scientific and Industrial Research (CSIR), New Delhi, India, for providing the Senior Research Fellowship (File No: 09/719 (0088)/2018-EMR-I). The authors also acknowledge Department of Science and Technology (DST), New Delhi, India, for sponsoring the HR-MS facility at BITS Pilani under the FIST program.

Disclosure statement

The authors declare no conflicts of interest.

Additional information

Funding

The authors acknowledge Birla Institute of Technology and Science, Pilani (BITS Pilani), Pilani Campus, Pilani, Rajasthan, India for providing NMR and other necessary laboratory facilities. Dr. S. N. C. Sridhar acknowledges the Council for Scientific and Industrial Research (CSIR), New Delhi, India, for providing the Senior Research Fellowship (File No: 09/719 (0088)/2018-EMR-I). The authors also acknowledge Department of Science and Technology (DST), New Delhi, India, for sponsoring the HR-MS facility at BITS Pilani under the FIST program.