Modulation of arachidonic acid metabolism by phenols: Relation to their structure and antioxidant/prooxidant properties

The effects of substituted catechols (3-methylcatechol, 4-methylcatechol, 4 -nitrocatechol, and guaiacol) and trihydroxybenzenes (pyrogallol, propyl ga llate, 1,2,4-trihydroxybenzene, and 1,3,5-trihydroxybenzene) on the synthes is of prostaglandin (PG)E-2, and leukotriene (LT)B-4, were tested in human A23187-stimulated polymorphonuclear leukocytes. The effects were related to their peroxyl-radical-scavenging (antioxidant), superoxide-scavenging (ant ioxidant), and superoxide-generating (prooxidant) properties. In general, c ompounds with hydroxyl groups in the ortho position increased PGE(2)/LTB4 r atio, and compounds with hydroxyl groups in the meta position decreased PGE (2)/LTB4 ratio. Catechols, which have hydroxyl groups in the ortho position , were the most potent peroxyl radical and superoxide anion scavengers. Tri hydroxybenzenes (pyrogallol, 1,2,4-trihydroxybenzene, and 1,3,5-trihydroxyb enzene) generated superoxide, whereas dihydroxybenzenes did not. Thus, the positions and number of hydroxyl groups seem to be the most important prope rties determining the action of phenolic compounds on PGE(2)/LTB4, ratio an d their antioxidant/prooxidant activities. (C) 1998 Elsevier Science Inc.