The effects of various stilbenes (i.e, 3,4',5-trihydroxystilbene, 3,4',5-trihydroxystilbene 3-O-D-glucoside and 2,3,4',5-tetrahydroxystilbene 2-O-D-glucoside) isolated from the roots of Polygonum species on rat peritoneal polymorphonuclear leukocyte lipoxygenase and cyclooxygenase activities were studied. Resveratrol (3,4',5-trihydroxystilbene) was found to inhibit the 5-lipoxygenase product, 5-HETE, and cyclooxygenase products, HHT and thromboxane B2; its concentrations for 50% inhibition (IC50) were 2.72 +/- 0.262 microM for the leukocyte lipoxygenase product, 5-HETE, 0.683 +/- 0.163 microM for the formations of HHT and 0.810 +/- 0.274 microM for the formation of thromboxane B2. Piceid (3,4',5-trihydroxystilbene 3-O-D-glucoside) and 2,3,4',5-tetrahydroxystilbene 2-O-D-glucoside also inhibited the formation of 5-HETE, HHT and thromboxane B2, although less strongly. Their IC50 values were, respectively, 55.3 +/- 15.3 microM and greater than 1000 microM for the formation of 5-HETE, 196.7 +/- 48.0 microM and 300.0 +/- 10.4 microM for the formation of HHT and 251.7 +/- 24.9 microM and 366.7 +/- 37.1 microM for the formation of thromboxane B2.