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Biological activity of 2-tert-butyl-1,4-benzoquinone (TBQ) and its derivatives, 2-tert-butyl-5-(2-propylthio)-1,4-benzoquinone, 2-tert-butyl-5- -(propylthio)-1,4-benzoquinone, 2-tert-butyl-5,6-(ethylenedithio)-1,4-benzoquinone, 2-tert-butyl-5-(phenylthio)-1,4-benzoquinone and 2-tert-butyl-6-(phenylthio)- 1,4-benzoquinone, were tested for their antioxidant, antibacterial, toxic, cytotoxic and genotoxic potential. Using the DPPH test, all derivatives showed good antioxidant activity, better than ascorbic acid, and the 2-tert- -butyl-5-(propylthio)-1,4-benzoquinone derivative showed the strongest effect. Better antibacterial potential was observed against Gram-positive bacteria in the broth microdilution method in which the 2-tert-butyl-5-(phenylthio)-1,4- -benzoquinone derivative showed the strongest activity (MIC = 15.6 μM). The results of toxicity tests, using the Brine shrimp test, indicated that the derivatives lose their toxic potential compared to TBQ, except for 2-tert-butyl-6- -(phenylthio)-1,4-benzoquinone, which showed a 3 times stronger effect. Cytotoxicity was assessed by the MTT assay in 24 and 72 h treatments in MRC-5, HS 294T and A549 cell lines in threefold decreasing gradient (11, 33 and 100 μM). Modifications potentiate the cytotoxic effect, and the strongest effect was observed with the 2-tert-butyl-5,6-(ethylendithio)-1,4-benzoquinone derivative. In addition, the genotoxic potential was examined in the MRC-5 cell line using the comet assay. All tested derivatives of TBQ showed a genotoxic effect at all applied subtoxic concentrations. In general, the chemical modifications of TBQ enhanced its biological activity.

In this paper, the previously synthesized Cu(II) complex ([CuL1(N3) (CH3OH)]BF4) with N,N,N-trimethyl-2-oxo-2-(2-(1-(thiazol-2-yl)ethylidene)- hydrazinyl)ethan-1-aminium chloride, has been characterized and its biological activity has been studied in detail. The Cu(II) complex consists of ligand coordinated in a deprotonated, formally neutral zwitter-ionic form, via NNO atoms, one azido ligand and one methanol molecule. The Cu(II) complex was selected due to results of the cytotoxic activity, the brine shrimp test and DPPH radical scavenging activity, which were previously performed. The effects of Cu(II) complex on cell cycle phase distribution of cervical adenocarcinoma HeLa cells were investigated in order to examine the mechanisms of its anticancer activity. The measurement of intracellular ROS levels in HeLa and HaCaT cell lines were evaluated in order to explore their possible generation and the role in cytotoxic activity. The possible anti-invasive and anti-angiogenic properties of Cu(II) complex were evaluated. DNA binding experiments, including fluorescence displacement study and DNA cleavage experiments, were performed in order to obtain information on the type of DNA-metal complex interactions.

In this paper, Cu(II), Mn(II) and Zn(II) complexes with N , N , N -trimethyl-2-oxo-2-(2-(1-(thiazol-2-yl)ethylidene)hydrazinyl)ethan-1-aminium chloride (HL1Cl) were synthesized and characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental analysis and DFT calculations. In all three complexes, a ligand (L1) is coordinated in a deprotonated formally neutral zwitterionic form via NNO donor set atoms. Cu(II) and Zn(II) form mononuclear penta-coordinated complexes [CuL1(N 3 )(CH 3 OH)]BF 4 and [ZnL1(N 3 ) 2 ], respectively, while Mn(II) forms a binuclear [Mn 2 L1 2 (μ- 1,1 -N 3 ) 2 (N 3 ) 2 ]·2CH 3 OH complex, with unusual distorted trigonal-prismatic geometry around the metal centers. The antimicrobial activity of these complexes was tested against a panel of Gram-negative and Gram-positive bacteria, two yeasts and one fungal strain. The binuclear Mn(II) complex showed antifungal activity of similar intensity to amphotericin B. Based on the results of the brine shrimp test and DPPH radical scavenging activity, the most active Cu(II) and Mn(II) complexes were selected for evaluation of cytotoxic activity against five malignant cancer cell lines (HeLa, A375, MCF7, PC-3 and A549) and one normal cell line HaCaT. Both complexes showed significant activity. It should be pointed out that the activity of the Mn(II) complex against the MCF7 breast cancer cell line is only slightly weaker than that of cisplatin, but with selectivity to the tumor cell line in comparison to normal HaCaT cells, which is non-existent in the case of cisplatin.