Plant-derived acetophenones with antiasthmatic and anti-inflammatory properties: Inhibitory effects on chemotaxis, right angle light scatter and actin polymerization of polymorphonuclear granulocytes

3-Methoxy- and 2-hydroxy-3-methyl substituted 4-hydroxyacetophenones and so me of the corresponding 4-O-glucosides revealed inhibitory activity on LTB4 -, fMLP- and PAF-induced chemotaxis of polymorphonuclear granulocytes (PMN) , Blocking of PMN myeloperoxidase (MPO), which is required for the intracel lular activation of acetophenones, caused a loss of activity. By in vitro a ctivation of apocynin (1) with human MPO and H2O2 and subsequent chromatogr aphic purification an apocynin-free fraction was obtained, which contained the major metabolite. The fraction showed strong anti-chemotactic activity, which was largely preserved despite of MPO-blockade, The influences on rig ht angle light scatter and actin polymerization in PMN demonstrate the inhi bitory effects of acetophenones on the cytoskeletal rearrangement after sti mulation with fMLP, Acetosyringenin (2) was shown to reduce mastoparan-indu ced PMN migration. The inhibition of receptor independent motility of PMN s uggests that the active metabolites of acetophenones may interfere with the post receptor signalling.