Isolation and structural analysis of the covalent adduct formed between a bis-amino mitoxantrone analogue and DNA: a pathway to major–minor groove cross-linked adducts

Abstract

The major covalent adduct formed between a ¹³C-labelled formaldehyde activated bis-amino mitoxantrone analogue (WEHI-150) and the hexanucleotide d(CG^5MeCGCG)₂ has been isolated by HPLC chromatography and the structure determined by NMR spectroscopy. The results indicate that WEHI-150 forms one covalent bond through a primary amine to the N-2 of the G₂ residue, with the polycyclic ring structure intercalated at the ^5MeC₃pG₄/G₁₀p^5MeC₉ site. Furthermore, the WEHI-150 aromatic ring system is oriented approximately parallel to the long axis of the base pairs, with one aliphatic side-chain in the major groove and the other side-chain in the minor groove. This study indicates that mitoxantrone derivatives like WEHI-150 should be capable of forming major–minor groove cross-linked adducts that will likely produce considerably different intracellular biological properties compared to known anthracycline and anthracenedione anticancer drugs.