A Biflavonoid from Luxemburgia nobilis as inhibitor of DNA Topoisomerases.

摘要

The biflavonoid 2'',3''-diidroochnaflavone ( 1), isolated from the leaves of Luxemburgia nobilis, was cytotoxic to murine Ehrlich carcinoma (IC (50) = 17.2 muM) and human leukemia K562 cells (IC (50) = 89.0 muM) in a concentration-dependent manner in 45 h cell culture. The acetyl ( 1a) and methyl ( 1b) derivatives of 1 were not cytotoxic to these tumour cells at 67.0 and 82.0 muM concentrations, respectively. Biflavonoid 1 as well 1a inhibit the activity of human DNA topoisomerases I and II-alpha as observed in relaxation and decatenation assays. In addition, we show that 1 is a DNA interacting agent, which causes DNA unwinding in an assay with topoisomerase I. Also, spectrophotometric titration of 1 with DNA resulted in a pronounced hypochromic effect.