Anti-inflammatory activities of two flavanones, sigmoidin A and sigmoidin B, from Erythrina sigmoidea

Two prenylated flavanones isolated from Erythrina sigmoidea Hua (sigmoidin A and sigmoidin B) were studied for their ability to inhibit the stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical and arachidonic acid metabolism. In addition, the compounds were studied in two experimental models of inflammation induced in mouse ears by 12- O-tetradecanoylphorbol 13-acetate (TPA) and the phospholipase A (2)-induced mouse paw oedema. Both sigmoidins A and B proved to be potent scavengers of the DPPH radical, while the study of the inhibition of arachidonic acid metabolism demonstrated that these same compounds were selective inhibitors of 5-lipoxygenase, with no effect on cyclooxygenase-1 activity. Dose-response inhibitor potency was established for sigmoidin A (IC (50) = 31 microM). In the assay of phospholipase A (2)-induced mouse paw oedema, only the sigmoidin B derivative inhibited oedema formation at 60 min, showing a percentage of inhibition below that obtained with cyproheptadine (59 % vs. 74 %). In the TPA test, sigmoidins A and B decreased the induced oedema by 89 % and 83 %, respectively. This is the first time that the anti-inflammatory activity and antioxidant properties of these prenylflavanones have been reported. The results indicate that the compounds have different mechanisms of action depending on whether one or two prenyl groups are present in ring B.