Abstract
The biflavonoid 2'',3''-diidroochnaflavone ( 1), isolated from the leaves of Luxemburgia nobilis, was cytotoxic to murine Ehrlich carcinoma (IC50 = 17.2 microM) and human leukemia K562 cells (IC50 = 89.0 microM) 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 microM 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.
MeSH terms
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Animals
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Antineoplastic Agents, Phytogenic / administration & dosage
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Antineoplastic Agents, Phytogenic / pharmacology*
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Antineoplastic Agents, Phytogenic / therapeutic use
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Biflavonoids / administration & dosage
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Biflavonoids / pharmacology
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Biflavonoids / therapeutic use
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Cell Line, Tumor / drug effects
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Dose-Response Relationship, Drug
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Enzyme Inhibitors / administration & dosage
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Enzyme Inhibitors / pharmacology*
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Enzyme Inhibitors / therapeutic use
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Humans
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Inhibitory Concentration 50
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Mice
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Ochnaceae*
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Phytotherapy*
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Plant Extracts / administration & dosage
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Plant Extracts / pharmacology*
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Plant Extracts / therapeutic use
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Topoisomerase I Inhibitors*
Substances
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Antineoplastic Agents, Phytogenic
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Biflavonoids
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Enzyme Inhibitors
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Plant Extracts
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Topoisomerase I Inhibitors