Cytotoxicity, redox cycling and photodynamic action of two naturally occurring quinones.
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 adenocarcinoma 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.
Johnson Inbaraj
J
J
School of Chemistry, Madurai Kamaraj University, Madurai, India.
Krishna
M C
MC
Gandhidasan
R
R
Murugesan
R
R
D000230:Adenocarcinoma; D000880:Anthraquinones / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D001943:Breast Neoplasms; D002470:Cell Survival; D004305:Dose-Response Relationship, Drug; D004492:Edetic Acid; D004578:Electron Spin Resonance Spectroscopy; D006801:Humans; D007194:India; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology; D013481:Superoxides / Q000032:analysis / Q000737:chemistry; D014407:Tumor Cells, Cultured / Q000187:drug effects
D000880:Anthraquinones; D010936:Plant Extracts; C402293:barleriaquinone II; D013481:Superoxides; C402292:barleriaquinone I; D004492:Edetic Acid