Schomburgkixanthone, a novel bixanthone from the twigs of Garcinia schomburgkiana.

A novel bixanthone, named schomburgkixanthone (1), was isolated from the twigs of Garcinia schomburgkiana, along with six known compounds, griffipavixanthone (2), 4-hydroxyxanthone (3), 2-hydroxyxanthone (4), 1,6-dihydroxyxanthone (5), 1,7-dihydroxyxanthone (6), and 1,3,5-trihydroxyxanthone (7). The structure of 1 was identified by the application of NMR and MS data analyses and comparison with previous reports. Compound 1 showed the most powerful inhibition of rat intestinal α-glucosidase, with IC₅₀ values of 0.79 for maltase and 1.81 mM for sucrase. Compound 2 most strongly inhibited sucrase, with an IC₅₀ value of 4.58 mM.