α-Glucosidase Inhibitory Activity from Ethyl Acetate Extract of Antidesma bunius (L.) Spreng Stem Bark Containing Triterpenoids

BACKGROUND: Buni (Antidesma bunius [L.] Spreng) has been used as a traditional antidiabetic agent in Asia. OBJECTIVE: The mechanism of antidiabetic properties was studied in this study by determine its α-glucosidase inhibitory activity. METHOD: Inhibition of α-glucosidase was performed in all fraction of Buni stem bark with acarbose and miglitol as standards. The half maximal inhibitory concentration (IC(50)) value of acarbose and miglitol was 5.75 and 59.76 μg/mL respectively while ethyl acetate (EtOAc) fraction was the most active fraction with IC(50) of 19.33 μg/mL. Three isolates (B1, B2, and B3) were found in the EtOAc fraction and elucidated by infrared, (1)hydrogen-nuclear magnetic resonance,(13) carbon-nuclear magnetic resonance, and two-dimensional nuclear magnetic resonance. RESULT: The chemical structures of the isolates were identified by the spectrum then compared with literature which concluded that B1 is friedelin, B2 is β-sitosterol, and B3 is betulinic acid. Inhibition of the α-glucosidase assay showed IC(50) values of B1, B2, and B3 were 19.51, 49.85, and 18.49 μg/mL, respectively. SUMMARY: α-Glucosidase inhibitory activity assay was performed in n-hexane, ethyl acetate (EtOAc), methanol fraction of Buni (Antidesma bunius (L.) Spreng) stem bark and miglitol. EtOAc fraction from the liquid chromatography has the highest inhibitory activity against α-glucosidase. The chemical structures of the isolates were identified by the spectrums infrared, (1)hydrogen-nuclear magnetic resonance,(13) carbon-nuclear magnetic resonance, and two-dimensional nuclear magnetic resonance, then compared with literature which concluded that B1 is friedelin, B2 is β-sitosterol, and B3 is betulinic acid. Betulinic acid and friedelin showed the highest α-glucosidase inhibitory activity. [Image: see text] Abbreviations used: IC(50): Half maximal inhibitory concentration; H-NMR: Hydrogen-nuclear magnetic resonance; C-NMR: Carbon nuclear magnetic resonance; 2D-NMR: Two dimensional-nuclear magnetic resonance; EtOH: Ethanol; EtOAc: Ethyl acetate; MeOH: Methanol; CHCl(3): Chloroform; DMSO: Dimethyl sulfoxide; EtF: Ethyl acetate fraction; Na(2)CO(3): Sodium carbonate; IR: Infrared; TGR5: Transmembrane G protein-coupled receptor 5; EC(50): Half maximal effective concentration