Effect of six flavonoid compounds from Ixeris sonchifolia on stimulus-induced superoxide generation and tyrosyl phosphorylation in human neutrophils

Background: Ixeris sonchifolia (Bge.) Hance is an herbal medication used in China as an analgesic. Methods: The effect of six flavonoid compounds isolated from Ixeris sonchifolia (Bge.) Hance on stimulus-induced superoxide generation and phosphorylation of tyrosine residues of protein in human neutrophils was investigated. The six compounds examined were luteolin 7-glucuronide methylester (LGME), luteolin 7-glucuronide ethylester (LGEE), luteolin 7-glucoside (LG), luteolin 7-glucopyranosyl-(1-->6) -glucoside (LGG6), luteolin 7-glucopyranosyl-(1 --> 2)-glucoside (LGG2) and apigenin 7-glucoside (AG). Results: When the cells were preincubated with these six flavonoids, the superoxide generation induced by N-formylmethionyl-leucyl-phenylalanine (fMLP) was significantly suppressed in a concentration -dependent manner. These flavonoids also suppressed the superoxide generation induced by arachidonic acid (AA). The rate of suppression by these flavonoids was AG>LG, LGG6, LGEE, LGG2>LGME. In case of the superoxide generation induced by phorbol 12-myristate 13-acetate (PMA), LG, LGG6 and AG suppressed the superoxide generation but LGME, LGEE and LGG2 gave no effect. When the cells were incubated with fMLP in the presence of LGME, LGEE and AG, fMLP-induced tyrosyl phosphorylation of 45-kDa proteins of the cells was dose-dependently suppressed in parallel to the suppression of fMLP-induced superoxide generation. Conclusion: Flavonoids suppress tyrosine phosphorylase in a dose-dependent manner, and may have pharmacoceutical applications. (C) 2002 Elsevier Science B.V. All rights reserved.