In silico studies of bioactive compounds from selected African plants with inhibitory activity against nitric oxide synthase and arginase implicated in asthma

Abstract

Background It is a known fact that arginine is a common substrate for arginase and nitric oxide synthase (NOS). However, an imbalance between both enzymes could lead to a change in airway responses. Reports suggest that increased activities of both enzymes could lead to airway hyper-responsiveness. Thus, the requests for NOS inhibitors that can also inhibit arginase as the elevated activities of both enzymes have detrimental consequence on airways in asthma. Bioactive compounds from Azadirachta indica, Crinum glaucum, and Mangifera indica are documented for anti-inflammatory, immunomodulatory, anti-histaminic, smooth-muscle relaxants, and anti-allergic potentials. However, the mechanisms of action of these bioactive compounds in conferring the aforementioned protections are not well characterized. The objective of this present study is to assess in silico inhibitory potentials of these bioactive compounds against NOS and arginase via binding at their active sites. The crystal structures of NOS and arginase were retrieved from the protein database, while the bioactive compounds were retrieved from PubChem. Drug-likeness of the selected bioactive compounds was assessed using DruLiTo software. The successful compounds were docked with active sites of enzymes using AutoDock Vina docking software, and the docked complexes were analyzed using LigPlot and protein-ligand profiler web server. Results The findings of the study revealed that the bioactive compounds from A. indica, C. glaucum, and M. indica were able to interact with the active sites of NOS and arginase with the exception of gallic acid (from M. indica) and nimbandiol (from A. indica); these compounds showed differential binding energies (kcal/mol) and a number of them had higher binding energies than l-arginine when docked with NOS. Conclusion Conclusively, the in silico analysis proposes that these compounds could prove to be probable anti-asthmatic drugs.