Bio-guided isolation of alpha-glucosidase inhibitory compounds from Vietnamese fruits: and studies

Garcinia schomburgkiana is an edible tree widely distributed in the southern region of Vietnam. Little is known about the alpha-glucosidase inhibition of the Vietnamese Garcinia schomburgkiana . The aim of the current study was to explore the anti-diabetic potential of G. schomburgkiana fruits. All the fractions of G. schomburgkiana were evaluated for alpha-glucosidase inhibition, followed by bioassay-guided isolation. A new compound, epi -guttiferone Q ( 1 ), together with ten known compounds, guttiferones I-K ( 2-3 ), hypersampsone I ( 4 ), sampsonione D ( 5 ), sampsonione H ( 6 ), β-mangostin ( 7 ), α-mangostin ( 8 ), 9-hydroxycalabaxanthone ( 9 ), and fuscaxanthone ( 10 ), were isolated and structurally elucidated. The structure of the new metabolite 1 was confirmed through 1D and 2D NMR spectroscopy, and MS analysis. To the best of our knowledge, the metabolites (except 3 ) have not been isolated from this plant previously. All isolated compounds were evaluated for their alpha-glucosidase inhibition. Compounds 1-6 showed potent activity with IC 50 values ranging from 16.2 to 130.6 μM. Compound 2 was further selected for a kinetic study. The result indicated that it was a competitive type. Additionally, in silico docking was employed to predict the binding mechanism of 1-2 and 4-6 in the active site of alpha-glucosidase, suggesting their potential as promising anti-diabetic compounds. Molecular dynamic simulation was also applied to 1 to better understand its inhibitory mechanism. Garcinia schomburgkiana is an edible tree widely distributed in the southern region of Vietnam.