Cytotoxicity, redox cycling and photodynamic action of two naturally occurring quinones.

J Johnson Inbaraj, M C Krishna, R Gandhidasan, R Murugesan

School of Chemistry, Madurai Kamaraj University, Madurai, India.

Biochimica et biophysica acta 1999 Nov 16

filter terms:

Two naturally occurring anthraquinones, barleriaquinone-I (BQ-I) and barleriaquinone-II (BQ-II), extracted from Barleria buxifolia, are tested for their cytotoxic action by aerobic incubation with human breast aden ocarcinoma cells (MCF7). Cytotoxicities, measured as LD(50) (50% inhibition of colony formation) values, show BQ-II to be more active than BQ-I. Electron paramagnetic resonance studies confirm that BQ-II is reductively activated by NADH:cytochrome c reductase to superoxide anion radical. Cyclic voltammetric studies show one quasi-reversible redox couple for both BQ-I and BQ-II. Also, aerobic solutions of both BQ-I and BQ-II on visible illumination generate reactive oxygen species. Formation of O*-2 is studied by both EPR spin trapping and SOD-inhibitable cytochrome c reduction techniques. BQ-I generates more singlet oxygen as evidenced from the photobleaching of N,N-dimethyl-4-nitrosoaniline.

Citation

J Johnson Inbaraj, M C Krishna, R Gandhidasan, R Murugesan. Cytotoxicity, redox cycling and photodynamic action of two naturally occurring quinones. Biochimica et biophysica acta. 1999 Nov 16;1472(3):462-70