Coumarin derivatives enhance the chemiluminescence accompanying lipid peroxidation

The effect of laser dyes, derivatives of 1,2-benzopyrone (coumarin), on the chemiluminescence (CL) accompanying Fe(2+)-induced lipid peroxidation (LPO) in liposomes prepared from egg yolk phospholipids has been investigated. It was found that quinolizin (9a,9,1-gh)-substituted coumarins enhanced CL at the stages of "fast" and "slow" flashes (abbreviated as FF and SF, respectively), which are known to accompany lipid hydroperoxide decomposition (FF) and chain LPO reaction development (SF). On the other hand, these compounds did not virtually change the shape of CL curve (in particular, lag phase duration) and accumulation of the LPO products reacting with 2-thiobarbituric acid (TBARS). The dependences of FF and SF amplitudes on the concentration of coumarins exhibited for some compounds an effect of saturation with subsequent decrease of CL at high concentrations of the dyes. The highest degree of CL amplification was reached with the compound 2,3,5,6-1H,4H-tetrahydro-9-(2'-benzoimidazolyl)-quinolizin- (9,9a,1-gh)coumarin (C-525), which enhanced CL at the stages of FF and SF by a factor 1600 at a dye concentration of 8 nmoles/mg of phospholipid. On the other hand, C-525 did not increase the intensity of CL associated with the decomposition of H2O2 by Fe2+ ions (Fenton's reaction). Apparently, these coumarin sensitizers may be used for selective enhancement of CL associated with LPO both in experimental and clinical investigations.