The first examples of
platinum(II) complexes of 3-(aminomethyl)naphthoquinone
Mannich bases have been synthesised and their crystal structures are described. Neutral and charged complexes have been obtained, fully characterised and their cytotoxic activities have also been investigated. 3-[(R(1)-amino)(pyridin-2-yl)methyl]-2-hydroxy-1,4-
naphthoquinones (R(1) = n-Bu, HL1; Bn, HL2; furfuryl, HL3; n-heptyl, HL4 and n-decyl, HL5) coordinate to
platinum(II) through the two
nitrogen atoms. The neutral complexes cis-[Pt(HL)Cl(2)] 1a-5a are analogous to
cisplatin with the bidentate
ligand HL and two
chlorine atoms occupying cis positions. In the charged complexes cis-[Pt(L(-))(NH(3))(2)]NO(3)1b-5b the deprotonated form of the
ligand L(-) also coordinates via the
nitrogen atoms, and the other two positions around the
platinum(II) ion are completed with NH(3)
ligands. The cytotoxic activities of all compounds have been tested for six different
cancer cell lines: MDA-MB-435 (
melanoma), HL-60 (promyelocytic leukaemia), HCT-8 (colon), SF-295 (brain), OVCAR-8 (ovary) and PC-3 (prostate). Proligands HL4 and HL5 have exhibited high activity against HL-60 (IC(50) = 1.9 and 3.8 μmol L(-1), respectively), HCT-8 (IC(50) = 1.6 and 1.7 μmol L(-1), respectively) and SF-295 (IC(50) = 1.1 and 1.7 μmol L(-1), respectively). The chlorido complexes 1a-5a have shown high to moderate cytotoxic activities, complex 4a (R(1) = n-heptyl) being more active than proligand HL4 against
melanoma (IC(50) = 6.4 and > 40 μmol L(-1), respectively) and more active than
cisplatin against all tested cell lines. Among the
amine charged complexes only 4b and 5b have exhibited significant cytotoxic activity against the tested cell lines, although they were only moderately active against the PC-3 cell line (IC(50) = 29.9 and 15.6 μmol L(-1), respectively). In general the compounds with the longest
carbon chains (R(1) = n-heptyl and n-decyl) have exhibited the highest activities.