Bioassay-guided isolation of prenylated xanthones and polycyclic acylphloroglucinols from the leaves of Garcinia nujiangensis.

Bioassay-guided fractionation of the acetone extract of the leaves of Garcinia nujiangensis resulted in the isolation of two new prenylated xanthones, nujiangexanthones A (1) and B (2), three new polycyclic polyprenylated acylphloroglucinols, nujiangefolins A-C (3-5), and 10 known related analogues. The structures of compounds 1-5 were elucidated by interpretation of their spectroscopic data. Compounds 3 and 4 are unusual polycyclic polyprenylated acylphloroglucinols in which the enol hydroxy group forms a six-membered ring with a benzene ring carbon. The compounds isolated were evaluated for their cytotoxic effects against 11 cancer cell lines and immortalized MIHA normal liver cells, and the test substances demonstrated selectivity toward the cancer cells. Isojacareubin (6) was found to be the most potent cytotoxic compound of those tested.