Antiproliferative activity of caged xanthones from the leaves of Garcinia wightii T. Anderson.

Two new caged xanthones, wightiic acid (1) 16-O-methyl wightiic acid (2), along with eight known compounds, gaudichaudic acid E (3), isogaudichaudic acid E (4), ursolic acid (5) stigmasterol (6), lupeol (7), glutinol (8), lupenone (9) and stigmasteryl linoleate (10) were isolated from Garcinia wightii T. Anderson. The structures of the compounds were elucidated by spectroscopic means, including 1D and 2D NMR, HR-ESIMS, and the absolute configuration of the new compounds 1 and 2 were determined by analysis of ECD data. Anti-proliferation activities of the four caged xanthones (1-4) were evaluated by MTT assay on MCF-7 and SKBR-3 human breast cancer cells and A-375 human melanoma cells by MTT assay. All the tested compounds exhibited dose dependent antiproliferative activity. Wightiic acid (1) showed remarkable activity with IC₅₀ value of 4.7 μM and 5.2 μM respectively in A-375 and MCF-7 cells. The compound isogaudichaudic acid E (4) induced potent antiproliferation against SKBR-3 cells with an IC₅₀ value of 6.1 μM.