Inhibitory effect of eight simple coumarins on the lucigenin enhanced chemiluminescence of rabbit neutrophils.

The generation of superoxide anion (O2*-) and other reactive oxygen species (ROS), such as HO*, HOCl, NO, 1O2 and H2O2, by stimulated polymorphonuclear leukocytes during phagocytosis is a major mechanism of host defense against invading microorganisms. However, large amounts of ROS are suggested to be responsible for many diseases. In this work we studied the inhibitory effect of eight simple coumarins on O2*- generation by rabbit neutrophil upon stimulation with opsonized zymosan, using lucigenin enhanced chemiluminescence assay. We observed that coumarins containing hydroxy or acetoxy substituents at position 7 of the benzopyrone ring were the most active ones (IC50 values ranging from 6.0 +/- 2.8 to 18.6 +/- 2.6 micromol/L). Substitution of these groups by allyloxy or metoxy groups decreased the activity and unsubstituted coumarin had no effect. Cell damage after exposure to 200 micromol/L of each compound was determined by measurement of the activity of the released cytosolic lactate dehydrogenase and by Trypan Blue dye exclusion test. None of the drugs affected significantly the cellular viability.