Effect of the Isocoumarin Paepalantine on the Luminol and Lucigenin Amplified Chemiluminescence of Rat Neutrophils

摘要

Paepalantine (9,10-dihydroxy-5,7-dimethoxy-1H-naphto(2,3c)pyran-1-one), a natural isocoumarin isolated from the capitula of Paepalanthus bromelioides (Eriocaulaceae), was assessed for its effect on the respiratory burst (zymosan-stimulated luminol-enhanced chemiluminescence and PMA-stimulated lucigenin-enhanced chemiluminescence) of polymorphonuclear neutrophils in vitro. Special attention was devoted to establishing the IC_(50) for neutrophils. Paepalantine was able to decrease luminol and lucigenin chemiluminescence, reflecting an inhibitory effect on the respiratory burst, with an ED_(50) of 0.44 ± 0.05 and 0.84 ± 0.15 μg/ml, respectively. A cell-free system was performed with paepalantine on myeloperoxidase/H_2O_2 and myeloperoxidase/H_2O_2/Cl~- systems. Paepalantine inhibited luminol oxidation in both systems. This inhibition was related to the interaction of paepalantine-myeloperoxidase and its scavenger effect on HOCl.