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= triphenylphosphine; Haptsc = 2-acetylpyridine-thiosemicarbazone; Hapmtsc = 2-acetylpyridine-N(4)-methyl-thiosemicarbazone and Happtsc = 2-acetylpyridine-N(4)-phenylthiosemicarbazone. All complexes were characterized by elemental analysis, IR, UV-Vis, 1 H and 31 P{ 1 H} NMR spectroscopies, and had their crystalline structures determined by X-ray diffractometry from single crystals. The monoanionic thiosemicarbazonate ligands act in a tridentate mode, binding to the metal through the pyridine nitrogen, the azomethine nitrogen and the sulfur atoms. The cytotoxic activity against the breast cancer cell line MDA-MB231 and the anti-Mycobacterium tuberculosis H 37 Rv ATCC 27294 activity were evaluated for the compounds. All Pd II complexes were highly active against the studied cell line, presenting similar values of IC 50 , around 5 μmol L -1 , while the clinically applied antitumor agent cisplatin was inactive. The compounds show remarkable anti-M. tuberculosis activities, presenting MIC values comparable or better than some commercial anti-M tuberculosis drugs.

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Tuberculosis (TB) is currently the leading cause of death related to infectious diseases worldwide, as reported by the World Health Organization. Moreover, the increasing number of multidrug-resistant tuberculosis (MDR-TB) cases has alarmed health agencies, warranting extensive efforts to discover novel drugs that are effective and also safe. In this study, 23 new compounds were synthesized and evaluated in vitro against the drug-resistant strains of M. tuberculosis. The compound 6-((3-fluoro-4-thiomorpholinophenyl)carbamoyl)benzo[c][1,2,5] oxadiazole 1-N-oxide (5 b) was particularly remarkable in this regard as it demonstrated MIC 90 values below 0.28 μM against all the MDR strains evaluated, thus suggesting that this compound might have a different mechanism of action. Benzofuroxans are an attractive new class of anti-TB agents, exemplified by compound 5 b, with excellent potency against the replicating and drug-resistant strains of M. tuberculosis.