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Mitoxantrone is a promising antitumor drug having considerably reduced cardiotoxicity as compared to anthracyclines. Its binding to deoxyhexanucleotides sequence d-(ATCGAT)2 has been studied by proton and phosphorous-31 nuclear magnetic resonance spectroscopy. The stoichiometry reveals that 1:1 and 2:1 mitoxantrone-d(ATCGAT)2 complexes are formed in solution. Significant upfield shifts in 6H/7H, 2H/3H, 11NH, and 12NH protons (∼.5 ppm) of mitoxantrone and T6NH imino protons (∼.3 ppm) are observed. The phosphorous resonances do not shift significantly indicating that the base pairs do not open at any nucleotide step along the sequence of hexamer. Several inter-molecular Nuclear Overhauser Enhancement connectivities between mitoxantrone and hexanucleotide protons indicate that mitoxantrone chromophore stacks with terminal A1-T6 base pair and side chains involving 12CH2, 12NH, and 14OH protons are in close proximity of A1, T2, A5, and T6 bases. Absorption and emission spectra show red shift in wavelength maxima, which is characteristic of stacking interaction. At higher mitoxantrone to nucleic acid ratios, electrostatic interactions are dominant. The 2:1 drug/DNA stoichiometric structure obtained by restrained Molecular Dynamics simulations shows considerable distortions in backbone torsional angles and helicoidal parameters although structural fluctuations in 25 ps analysis of trajectory are found to be negligible. Mitoxantrone binds as a monomer at either or both ends of hexamer externally with side chains interacting specifically with DNA. The findings are relevant to the understanding of pharmacological action of drug.

Numbers of drugs are being synthesized every year to meet the target of safe and disease-free society. Presently molecular modeling technique is used to unfold the mechanism of action of drugs alone or in conjunction with experimental methodologies. There are a number of drugs which are successfully developed using this methodology. Mitoxantrone (MTX) - 1, 4-dihydroxy-5, 8-bis {[2-(2-hydroxyethyl) amino] amino}-9, 10-anthracenedione is marketed under the name Novantrone, an anticancer drug used in chemotherapy. Its important analog ametantrone and various other analogs differ from one another in the position of side chain or functionalities on the chromophore eventually exhibit varied biological activities. DNA binding is an important phenomenon for anticancer activity of these drugs. In order to understand the interactions of the drug molecules with its receptor site, at atomic level, we have carried out computer simulations of drug and DNA alone and also in complex mode in water as a medium. All the simulations are being carried out using molecular operating environment (MOE) and X3DNA software tools on SUN SOLARIS platform. Interaction energy of all the drug molecules with DNA is determined and compared. Also the structural changes in DNA and drug before and after complex formation are studied extensively.