Inhibition mechanism of alpha-amylase, a diabetes target, by a steroidal pregnane and pregnane glycosides derived from Gongronema latifolium Benth

Abstract

Alpha-amylase is widely exploited as a drug target for preventing postprandial hyperglycemia in diabetes and other metabolic diseases. Inhibition of this enzyme by plant-derived pregnanes is not fully understood. Herein, we used in vitro, in silico, and in vivo studies to provide further insights into the alpha-amylase inhibitory potential of selected pregnane-rich chromatographic fractions and four steroidal pregnane phytochemicals (SPPs), viz: marsectohexol (P1), 3-O-[6-deoxy-3-O-methyl-β-D-allopyranosyl-(1→14)-β-D-oleandropyranosyl]-11,12-di-O-tigloyl-17β-marsdenin (P2), 3-O-[6-deoxy-3-O-methyl-β-D-allopyranosyl-(1→4)-β-D-oleandropyranosyl]-17β-marsdenin (P3), and 3-O-[6-deoxy-3-O-methyl-β-D-allopyranosyl-(1→4)-β-D-canaropyranosyl]-17β-marsdenin (P4) derived from Gongronema latifolium Benth. The results revealed that the SPPs source pregnane-rich chromatographic fractions and the SPPs (P1–P4) exhibited inhibitory potential against porcine pancreatic alpha-amylase in vitro. Compounds P1 and P2 with IC50 values 10.01 and 12.10 µM, respectively, showed greater inhibitory potential than the reference acarbose (IC50 = 13.47 µM). Molecular docking analysis suggests that the SPPs had a strong binding affinity to porcine pancreatic alpha-amylase (PPA), human pancreatic alpha-amylase (HPA), and human salivary alpha-amylase (HSA), interacting with the key active site residues through an array of hydrophobic interactions and hydrogen bonds. The strong interactions of the SPPs with Glu233 and Asp300 residues may disrupt their roles in the acid-base catalytic mechanism and proper orientation of the polymeric substrates, respectively. The interactions with human pancreatic amylase were maintained in a dynamic environment as indicated by the root mean square deviation, radius of gyration, surface accessible surface area, and number of hydrogen bonds computed from the trajectories obtained from a 100-ns molecular dynamics simulation. Key loop regions of HPA that contribute to substrate binding exhibited flexibility and interaction potential toward the compounds as indicated by the root mean square fluctuation. Furthermore, P1 significantly reduced blood glucose levels and area under the curve in albino rats which were orally challenged with starch. Therefore, Gongronema latifolium and its constituent SPPs may be exploited as inhibitors of pancreatic alpha-amylase as an oral policy for impeding postprandial blood glucose rise.

Pancreatic biomarkers: role in diabetes mellitus

“…The results suggest that Gongronema latifolium and its constituent SPPs could be used as oral agents to prevent the increase in postprandial blood glucose levels due to their ability to inhibit pancreatic alpha-amylase. [42] However, α-amylase also contributes to postprandial hyperglycemia by increasing blood sugar levels. Therefore, the inhibition of α-amylase has become a target for the treatment and management of postprandial blood glucose increases.…”

Structural insights into the binding of zoledronic acid with RANKL via computational simulations

“…Prior to molecular docking, ZOL was prepared by adding the polar hydrogen atoms and designating Gasteiger charges, according to physiological pH 7.4. Meanwhile, we added the polar hydrogen atoms and assigned Kollman charges on RANKL as well (Wang et al, 2021;Kumar et al, 2022;Ogunyemi et al, Frontiers in Molecular Biosciences frontiersin.org 2022). Then we input the processed coordinate files into AutoDockTools v1.5.6 and converted this into PDBQT format files, which were needed in the follow-up docking simulation.…”

Direct Estimate of the Specificity Constant: A Possibility or a Fluke? Pre-steady-state Substrate Concentrations and Enabling Mathematical Equations

“…The waste to wealth concept is best achieved industrially upon application of a kinetic model; thus, research has focused on how best to convert cellulose to the precursors of biofuels [8][9][10][11] and possibly solvents for other applications in the pharmaceutical and food industries. The control of diabetes has prompted recent studies on the digestibility of recalcitrant starch and the inhibition mechanism of alphaamylase [12][13][14][15].…”