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 effect in obese rats. Thus, this study
sought to investigate the in vitro and in silico effects of fractions from Alstonia boonei stem bark on selected obesityrelated
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 profiled 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 effect 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 identified in the CAF and CSF using LCMS/
MS. The CAF and CSF revealed good inhibitory activity against pancreatic lipase enzyme, but weak and good activity
against amylase respectively while only CSF had inhibitory activity against α-glucosidase. Both fractions showed
antiadipogenic effect in the clearance of adipocytes and reduction of lipid content in 3T3-L1 adipocytes. The LCMS/
MS identified 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 orlistat).
The best two docked compounds to the three enzymes were firmly 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 nucleophile
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-phenylpropionate
(-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.
