“…This would show the relevance of the planar naphthalenic group for the cytotoxic–antineoplastic activity, probably due to which it would allow a better intercalating association when they act as non‐covalent binders of DNA . In spite of the fact that the amino acid moiety does not significantly modify the bioactivity previously reported for naphthohydroquinones , it is interesting to note that the GI 50 values of compounds 4a – 8a against MCF‐7 breast cancer cells are very close to that of the standard drug doxorubicin and even slightly better for the phenylalanine derivative 6a . Furthermore, compounds 4a – 8a are more cytotoxic than several conjugates reported in the literature such as platinum complexes of enantiomerically pure α‐trifluoromethyl alanine , 1,4‐bis(2‐aminoethylamino)anthraquinone–, ametantrone–, and mitoxantrone–amino acid conjugates and more than naphthalimide–leucine conjugates against A‐549 and/or MCF‐7 cells. - In the group of purine–naphthohydroquinone conjugates 10 – 13 , the fully aromatized compounds 10a – 13a (GI 50 2.9–8.7 μM) also showed higher cytotoxicity than the corresponding 5,8‐dihydro‐ ( 10b – 13b ) or 5,6,7,8‐tetrahydro‐ ( 10c – 13c ) derivatives against A‐549 or HT‐29 cultured cells.
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