Interaction of mitoxantrone with human serum albumin: Spectroscopic and molecular modeling studies

Mitoxantrone (MTX) is a clinically used antitumor anthracycline, which is made available to the target tissues by transport protein human serum albumin (HSA). Being less toxic unlike other member of this family, its binding characteristics are therefore of immense interest. The circular dichroism (CD), fluorescence and Fourier transform infrared (FTIR) spectroscopies were employed to elucidate the mode and the mechanism for this interaction. MTX binding is characterized by one high affinity binding site with the association constants of the order of 10⁵. Correlation between stability of N-MTX (drug bound N form of HSA) and B-MTX (drug bound B form of HSA) complexes with drug distribution has been discussed. The molecular distance, r, between donor (HSA) and acceptor (MTX) was estimated according to Forster's theory of non-radiation energy transfer. The features of MTX induced structural perturbation of human serum albumin (HSA) has been studied in detail by CD and FTIR analysis. Domain I was assigned to possess high affinity binding site for MTX. Molecular docking showed that the MTX binds HSA to a non-classical drug binding site. The binding dynamics was expounded by synchronous fluorescence, thermodynamic parameters and molecular modeling, which entails that hydrophobic interactions, hydrogen bonding and electrostatic forces, stabilizes the interaction.