Phytochemical analysis, in vitro and in silico efects from Alstonia boonei De Wild stem bark on selected digestive enzymes and adipogenesis in 3T3-L1 preadipocytes

Abstract

Background Obesity is a global health issue arising from the unhealthy accumulation of fat. Medicinal plants such as Alstonia boonei stem bark has been reported to possess body weight reducing efect in obese rats. Thus, this study sought to investigate the in vitro and in silico efects of fractions from Alstonia boonei stem bark on selected obesity related digestive enzymes and adipogenesis in 3T3-L1 preadipocytes. Method Two fractions were prepared from A. boonei: crude alkaloid fraction (CAF) and crude saponin fraction (CSF), and their phytochemical compounds were profled using Liquid chromatography with tandem mass spectrometry (LCMS/MS). The fractions were assayed for inhibitory activity against lipase, α-amylase and α-glucosidase, likewise their antiadipogenic efect in 3T3-L1 adipocytes. The binding properties with the 3 enzymes were also assessed using in silico tools. Results Eleven alkaloids and six saponin phytochemical compounds were identifed in the CAF and CSF using LCMS/ MS. The CAF and CSF revealed good inhibitory activity against pancreatic lipase enzyme, but weak and good activ‑ ity against amylase respectively while only CSF had inhibitory activity against α-glucosidase. Both fractions showed antiadipogenic efect in the clearance of adipocytes and reduction of lipid content in 3T3-L1 adipocytes. The LCMS/ MS identifed compounds (41) from both fractions demonstrated good binding properties with the 3 enzymes, with at least the top ten compounds having higher binding energies than the reference inhibitors (acarbose and orl‑istat). The best two docked compounds to the three enzymes were frmly anchored in the substrate binding pockets of the enzymes. In a similar binding pattern as the reference acarbose, Estradiol-17-phenylpropionate (-11.0 kcal/mol) and 3α-O-trans-Feruloyl-2 α -hydroxy-12-ursen-28-oic acid (-10.0 kcal/mol) interacted with Asp197 a catalytic nucleo‑ phile of pancreatic amylase. Estradiol-17-phenylpropionate (-10.8 kcal/mol) and 10-Hydroxyyohimbine (-10.4 kcal/mol) interacted with the catalytic triad (Ser152-Asp176-His263) of pancreatic lipase while Estradiol-17-phenylpropi‑onate (-10.1 kcal/mol) and 10-Hydroxyyohimbine (-9.9 kcal/mol) interacted with Asp616 and Asp518 the acid/base and nucleophilic residues of modelled α-glucosidase