Pauferrol A, a novel chalcone trimer with a cyclobutane ring from Caesalpinia ferrea mart exhibiting DNA topoisomerase II inhibition and apoptosis-inducing activity

Pauferrol A (1), a unique chalcone derivative was isolated from the stems of Caesalpinia ferrea Mart, and the structure was determined on the basis of 2D-NMR spectroscopy to be a chalcone trimer fused by a cyclobutane ring. This new chalcone trimer showed potent inhibitory activity against human topoisomerase II, with an IC50 value of 2.1 mu M, and cell proliferation inhibitory activity through the induction of apoptosis in human leukemia HL60 cells, with an IC50 value of 5.2 mu M. To our knowledge, this is the first report of the isolation and structure of this chalcone trimer and its biological activity. (C) 2007 Elsevier Ltd. All rights reserved.