New α -glucosidase inhibitory xanthones from the fruits of Garcinia schomburgkiana

Two previously unreported xanthones, xanthoschomes A and B (1 and 2), along with six known xanthones, α-mangostin (3), β-mangostin (4), γ-mangostin (5), garcinone C (6), 2-(γ,γ-dimethylallyl)-1,7-dihydroxy-3-methoxyxanthone (7), and dulxanthone D (8), have been isolated from the fruits of Vietnamese Garcinia schomburgkiana. The structures of all isolated compounds were fully characterised using spectroscopic data and comparison with the previous literature. All isolated compounds were evaluated for their in vitro α-glucosidase inhibitory activity. Compounds 1–8 demonstrated effective α-glucosidase inhibition, with the IC₅₀ ranging from 2.91 to 26.0 μM, outperforming the standard acarbose (IC₅₀ 179 μM). Among these isolated compounds, compound 8 exhibited the highest inhibitory activity against α-glucosidase, with an IC₅₀ value of 2.91 μM.