ABSTRACT
Drugs containing an anthraquinone moiety such as daunorubicin (Daunoblastin) and mitoxantrone (Onkotrone) constitute some of the most powerful cytostatics. They suppress tumor growth mainly by intercalation into DNA and inhibition of topoisomerase II, and are suspected to generate free radicals leading to DNA strand scission. We established a novel strategy for obtaining new highly functionalized derivatives of emodin (1,3,8-trihydroxy-6-methyl-anthraquinone). Using emodin, DIB, and an appropriate amine as starting materials, we obtained a wide range of emodin-related structures by one-pot synthesis. Several of these derivatives showed stronger cytotoxic and cytostatic activity than emodin. In particular, compound 6 was highly effective on the HepG2 tumor cell line, but did not show any cytotoxicity on normal hepatocytes. In addition to this favorable feature, compound 6 revealed interesting binding properties to a recombinant fragment of the multi-drug-resistance transporter, pgp, and reversed the multi-drug-resistance phenotype of H4-II-E cells, thus making this compound a promising potential anti-tumor drug.
Subject(s)
Emodin/chemical synthesis , Emodin/pharmacology , Animals , Cell Line, Tumor , Cell Survival/drug effects , Cell Survival/physiology , Dose-Response Relationship, Drug , Drug Evaluation, Preclinical/methods , Hepatocytes/drug effects , Hepatocytes/physiology , Humans , RatsABSTRACT
Flavonoids are well known to inhibit the function of the multi-drug-resistance (mdr) transporter by interacting with their ATP binding domains. The precise orientation of these molecules inside the ATP binding pocket is still unclear. We applied the saturation transfer difference (STD) NMR technique to investigate the binding of the flavonoid luteolin and its 7-O-beta-D-glycopyranoside to the recombinant nucleotide binding domain (NBD2) of mouse-mdr. First, this NMR technique confirmed binding of both ligands to NBD2, as was determined from tryptophan fluorescence-quenching experiments. Further, the results suggest binding of both luteolin and its 7-O-beta-D-glycopyranoside by their polar groups at positions 4, 5, and 3' to the protein.
Subject(s)
ATP Binding Cassette Transporter, Subfamily B/chemistry , ATP Binding Cassette Transporter, Subfamily B/metabolism , Luteolin/chemistry , Luteolin/metabolism , Animals , Drug Resistance , Ligands , Mice , Molecular Structure , Nuclear Magnetic Resonance, Biomolecular/methods , Nucleotides/chemistry , Protein Binding/physiology , Recombinant Proteins/chemistry , Recombinant Proteins/metabolism , Sensitivity and Specificity , ATP-Binding Cassette Sub-Family B Member 4ABSTRACT
To investigate the structural basis for the antioxidative effects of plant flavonoids on the lipid molecules of cellular membranes, we have studied the location and distribution of five different flavonoid molecules (flavone, chrysin, luteolin, myricetin, and luteolin-7-glucoside) with varying polarity in monounsaturated model membranes. The investigated molecules differed in the number of hydroxyl groups attached to the polyphenolic benzo-gamma-pyrone compounds. To investigate the relation between hydrophobicity and membrane localization/orientation, we have applied (1)H magic angle spinning NMR techniques measuring ring current induced chemical shift changes, nuclear Overhauser enhancement cross-relaxation rates, and lateral diffusion coefficients. All investigated flavonoids show a broad distribution along the membrane normal with a maximum in the lipid/water interface. With increasing number of hydroxyl groups, the maximum of this distribution is biased towards the lipid headgroups. These results are confirmed by pulsed field gradient NMR measurements of the lateral diffusion coefficients of phospholipids and flavonoids, respectively. From the localization of different flavonoid protons in the membrane, a model for the orientation of the molecules in a lipid bilayer can be deduced. This orientation depends on the position of the polar center of the flavonoid molecule.
