A new cytotoxic cyclopenta[b]benzofuran derivative, aglaiformosanin (1) and
three known cyclopenta[b]benzofuran derivatives (2-4) were isolated from t
he stem bark of Aglaia formosana. Compounds 1-4 exhibited potent cytotoxici
ty against the P-388, KB, HT-29, HL-60, and A549 cell lines. The structure
of compound I was determined by spectroscopic analysis.