The lipoxygenases (LOX) are a family of non-heme iron-containing dioxygenases which catalyze the stereospecific insertion of molecular oxygen lino arachidonic acid, leading to hydroxy derivatives as end products. In this work, we studied the behavior of seven isoflavans on 15-soybean lipoxygenases (15-sLOX), comparing them with the known inhibitors quercetin and 3,4-dihydroxybenzoic acid. Four of the seven investigated isoflavans showed IC50 values smaller than 50 mu M, being more potent than quercetin or 3, 4-dihydroxybenzoic acid. Besides a catecholic pattern, the presence of an aromatic ring B seems to confer additional activity to these compounds, a result which was rationalized by docking studies of these isoflavanss into the enzyme binding site.