Ricinelaidic acid, a 12-hydroxy fatty acid,is a leukotriene B4 (LTB4) receptor antagonist with the Ki of 2 µM in porcine neutrophil membranes. Ricinelaidic acid inhibits chemotaxis and calcium flux induced by LTB4 in isolated human neutrophils (IC50=10 and 7 µM, respectively). Ricinelaidic acid inhibits bronchoconstriction induced by LTB4 in rats[1].