Tetrahydrofuran lignans from Illicium floridanum and their activity in a luminol enhanced chemiluminescence assay

Two lignans of the tetrahydrofuran type, di-O-methyltetrahydrofuroguaiacin B (1) and (+)-veraguensin (2) were isolated from fruits and leaves of Illic ium floridanum Ellis (Illiciaceae). These compounds are the first genuine l ignans isolated from the genus Illicium. We investigated their radical scav enging potency towards 1,1-diphenyl-2-picrylhydrazyl radical reagent and th eir influence on luminol enhanced chemiluminescence (CHL) induced by differ ent stimuli in human polymorphonuclear neutrophils (PMN). Both compounds we re inactive in the TLC assay for chemical radical scavenge. In the PMN assa y, the symmetric lignan 1 at concentrations below 1.0 muM displayed a stron g inhibition of CHL induced by N-formyl-methionyl-leucyl-phenylalanine (fML P). At concentrations above 5 muM, 1 led to a pronounced increase of fMLP i nduced CHL. When CHL was stimulated with opsonized zymosan, both compounds were completely inactive. Thus, 1 must interfere selectively with a step in the signal cascade evoked by fMLP. In addition to their known PAF-receptor antagonism tetrahydrofuran lignans may thus also interfere with inflammato ry reponses by inhibition of free radical formation.