Study of DNA interactions with cyclic chalcone derivatives by spectroscopic techniques.

A series of chalcone derivatives (1-4) were studied. The interaction between these ligands and calf thymus DNA was studied with UV-vis spectrophotometry, fluorescence and circular dichroism spectroscopy. The binding constants K were estimated at 0.5-4.6×10(5) M(-1). All these measurements indicated that the compounds behave as effective DNA-intercalating agents. Electrophoretic separation proved that ligands inhibited topoisomerase I at a concentration of 60 µM.

Comparison of effects of some cyclic chalcone analogues on selected mitochondrial functions.

In earlier studies, cytotoxity of chalcones (1) and cyclic chalcone analogues E-2-arylidene-tetralones (2) and -benzosuberones (3) towards various murine and human tumour cells has been tested. Preliminary biochemical investigations showed the compounds to inhibit protein and DNA syntheses. It was also found that the compounds affect the cellular thiol status of the treated cells. In order to gain new insights into the cytotoxic mechanism of the compounds effects of some previously investigated 2 and 3 derivatives on isolated rat liver mitochondria was investigated. It was found that the most cytotoxic compounds 2c and 3b significantly decreased the GSH level of the mitochondria. Incubation of the investigated chalcones with reduced GSH under cell-free conditions indicated spontaneous conjugation (non-redox) reaction at pH 7.4 and pH 9.0. Investigation of antioxidant capacity of the compounds by monitoring time course of the Fenton-reaction initiated in vitro degradation of 2-deoxyribose showed the compounds to display hydroxyl radical scavenger activity. Investigation of respiratory control ratio of 2c and 3b showed the compounds to display an inhibitory effect on respiration, compound 2b, however, displayed rather an uncoupling effect. The experiments provide further details of cytotoxic effects of the synthetic chalcones displaying dual - cytotoxic and cytoprotective - effects.

In vitro effect of stobadine on Fe(2+)-induced oxidative stress in rat liver mitochondria.

The authors have studied the susceptibility of two key protective enzymes, glutathione peroxidase (GPX) and glutathione reductase (GR) to the reactive oxygen species (ROS) known to induce oxidative damage in vitro system containing Fe2+/EDTA. The ability of ROS scavanger stobadine to prevent oxidative damage was also studied. Incubation of GPX with Fe2+/EDTA resulted in the significant decrease in its enzyme activity while under the same condition the activity of GR was not changed. The presence of stobadine was effective in protecting GPX from the loss of its activity by in vitro oxidizing agents. The monitoring of the mitochondrial outer membrane dynamics by the method of synchronous fluorescence fingerprint showed that the membrane is involved in these processes. (Fig. 3, Ref. 35.)

[Fe2+-induced oxidative processes in the liver mitochondria of rats]. / Oxidacné procesy mitochondrií pecene potkana indukované Fe2+.

The study investigated the prooxidative in vitro effect of various Fe(2+)-EDTA concentrations on biochemical parameters of the energetic metabolism of rat liver mitochondria. Fe(2+)-EDTA was added in concentrations 150, 300 and 400 mmol/mg of mitochondrial protein. The study included the investigation of consumption of oxygen in state 4 (without ADP addition) and in state 3 (with ADP addition), and the activities of ATP-ase, superoxide dismutase (SOD) and glutathione reductase. The mitochondrial outer membrane dynamics were simultaneously monitored by the method of synchronous fluorescence fingerprint. When compared with the control group, the results imply that in state 4, the addition of 150 mmol of Fe2+/mg of mitochondrial protein caused an insignificant increase in respiration to 104%, whereas in state 3, the oxygen consumption was insignificantly inhibited to 82%. The activity of ATPase was insignificantly raised to 105%, whereas the superoxide dismutase activity has decreased significantly to 77%. The activity of glutathione reductase increased significantly to 124%. The addition of 300 mmol of Fe2+/mg of mitochondrial protein has caused a significant inhibition of oxygen consumption to 67% in state 4 and to 31% in state 3. The activity of ATPase showed an insignificant elevation to 104%. The activity of superoxide dismutase was significantly reduced to 52% and that of glutathione reductase dropped to 72%. The addition of 400 Fe2+/mg of mitochondrial protein strongly diminished the oxygen consumption to 36% in state 4, and similarly to 37% in state 3. The activity of ATP-ase was significantly decreased to 39%, the superoxide dismutase activity diminished to 17% and glutathione reductase activity dropped to 37%. The monitoring of the mitochondrial outer membrane by the analysis of synchronous fluorescence fingerprint showed that the membrane is involved in these processes. (Fig. 5, Ref. 12.)