Scalemic Caged Xanthones Isolated from the Stem Bark Extract of Garcinia propinqua

Seven new caged xanthones, doitunggarcinones
E–K (1–7), all as scalemic
mixtures and 10
known compounds (8–17), were isolated
from the stem bark extract of Garcinia propinqua. The structures were elucidated on the basis of spectroscopic methods.
The separation of the enantiomers of 1–6 was achieved by semipreparative chiral HPLC. The absolute configuration
of compound (+)-1 was determined by single-crystal X-ray
crystallographic analysis using Cu Kα radiation. The absolute
configurations of the other related compounds were determined from
comparisons of their ECD spectra with that of compound (+)-1. Compounds (−)-6 and 7 showed cytotoxicity
against a colon cancer cell line with IC50 values of 14.23
and 23.95 μM, respectively.