Naphthoquinones from Catalpa bungei “Jinsi” as potent antiproliferation agents inducing DNA damage

Structure-guided isolation of a CH2Cl2-soluble fraction of the heartwood of Catalpa bungei "Jinsi" provided two new naphthoquinones, 9-hydroxy-4-oxo-α-lapachone (1) and 6-hydroxy-4-oxo-α-lapachone (2), together with three undescribed ones (3-5) and six known ones (6-11). The structures were elucidated on the basis of spectroscopic methods including electronic circular dichroism calculation. The antiproliferative effects of these isolates were evaluated in human breast adenocarcinoma cells MCF7. (4R)-4,9-dihydroxy-α-lapachone (5) and (4S)-4,9-dihydroxy-α-lapachone (6) exhibited the significant activities with IC50 values of 2.19 and 2.41 μM, respectively. The structure-activity relationship of 1-11 in the antiproliferative assay was then discussed. The most potent 5 and 6 were found to induce cell arrest in G1 phage through DNA damage. The findings provided some valuable insights for the discovery and structural modification of α-lapachone as antiproliferative lead compounds against human breast adenocarcinoma cells.