Molecular dynamics study of stigmasterol and beta-sitosterol of Morinda citrifolia L. towards α-amylase and α-glucosidase.

Previous in vivo studies of Morinda citrifolia (Rubiaceae) reported that the extract inhibited α-amylase and reduced blood glucose levels in streptozotocin-induced diabetes mice. Moreover, molecular docking studies confirmed that ursolic acid and sterol compounds contained in the fruit interacted with important residues in the binding site of α-amylase and α-glucosidase. Our work aimed to study the complex stability of stigmasterol (which has been isolated from the M. citrifolia fruit for the first time) and beta-sitosterol towards α-amylase and α-glucosidase by employing molecular dynamics simulation on GROMACS 2016.3 embedded with the AMBER99SB-ILDN force field. The simulation was carried out for 100 ns at 310 oK. Based on the RMSD and RMSF graphs, the complexes of stigmasterol/α-amylase and stigmasterol/α-glucosidase are more stable compared to acarbose, the known inhibitor of both enzymes. Moreover, beta-sitosterol indicates a better stability complex with α-glucosidase compared to that of acarbose. Interestingly, the affinity of stigmasterol and beta-sitosterol to both enzymes, in terms of the total binding energy, is stronger than that of acarbose. Taken together, stigmasterol and beta-sitosterol in M. citrifolia fruit may have the potency to be developed as α-amylase and α-glucosidase inhibitors.Communicated by Ramaswamy H. Sarma.

Molecular docking and molecular dynamics studies of bioactive compounds contained in noni fruit (Morinda citrifolia L.) against human pancreatic α-amylase.

Human pancreatic α-amylase inhibition is currently a promising therapeutic target against type 2 diabetes (DMT2) because it can reduce aggressive digestion of carbohydrates into absorbable monosaccharides. In Indonesia, medicinal plants, e.g. Morinda citrifolia fruit, have been empirically utilized as a blood-sugar reducer, however, the inhibitory activity of compounds in this plant against human pancreatic α-amylase is still limited or none. Therefore, this study aimed to test the interaction of 7 compounds (americanin, asperulosidic acid, damnacanthal, quercetin, rutin, scopoletin, and ursolic acid) contained in noni fruit against human pancreatic α-amylase by molecular docking and molecular dynamics and compared their binding modes with that of acarbose. Results of the molecular docking simulation indicated that the ursolic acid compound possesses the best binding energy (-8.58 kcal/mol) and comparable to that of acarbose (-8.59 kcal/mol). The molecular dynamics study at 100 ns simulation, the values of RMSD, RMSF, the radius of gyration (Rg), the solvent-accessible surface area (SASA), principal component analysis (PCA), and MM-PBSA binding free energy were stable and identical to those of acarbose. It could be concluded that ursolic acid might be potential in inhibiting human pancreatic α-amylase, thus, potential to be developed as an anti-DMT2 drug candidate. Communicated by Ramaswamy H. Sarma.