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Here, we describe the synthesis, characterization, and in vitro biological evaluation of a series of transition metal complexes containing benzothiazole aniline (BTA). We employed BTA, which is known for its selective anticancer activity, and a salen-type Schiff-based ligand to coordinate several transition metals to achieve selective and synergistic cytotoxicity. The compounds obtained were characterized by NMR spectroscopy, mass spectrometry, Fourier transform infrared spectroscopy, and elemental analysis. The compounds L, MnL, FeL, CoL, and ZnL showed promising in vitro cytotoxicity against cancer cells, and they had a lower IC50 than that of the clinically used cisplatin. In particular, MnL had synergistic cytotoxicity against liver, breast, and colon cancer cells. Moreover, MnL, CoL, and CuL promoted the production of reactive oxygen species in HepG2 tumor cell lines. The lead compound of this series, MnL, remained stable in physiological settings, and docking results showed that it interacted rationally with the minor groove of DNA. Therefore, MnL may serve as a viable alternative to platinum-based chemotherapy. [ABSTRACT FROM AUTHOR]

The synthesis of two bifunctional chelates, 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A) conjugates of benzothiazoles (H3L3a and H3L3b), and the corresponding gadolinium complexes (GdL3a and GdL3b) was achieved. The intracellular and tumor-specific nature of GdL3a and GdL3b were confirmed by magnetic resonance images of the cytosols and nuclei of various cell lines. The two complexes displayed antitumor activities with varying degrees of growth-inhibition and total-growth-inhibition values depending on the types of tumor cells. They caused morphological changes in tumor cell lines at much lower concentrations of gadolinium ([Gd] ≥ 50 μ M) than their predecessors, DO3A-( p-aniline benzothiazole) conjugates (H3L1), and its GdIII complex (GdL1) required concentrations that were almost four times as high ([Gd] ≥ 200 μ M). [ABSTRACT FROM AUTHOR]