Wogonin (WG), wogonoside (WGS), and 3,5,7,2',6'-pentahydroxyl flavanone (PHF) were isolated from Scutellaria baicalensis, and their effects on histamine, leukotriene B(4) (LTB(4)), and immunoglobulin E (IgE) were examined in rats, observing for a manifestation of a type I allergic reaction. WG and WGS in the amounts of 10 and 100 microM were shown to markedly inhibit histamine release in cells stimulated with calcium ionophore A23187 or compound 48/80. PHF exerted inhibitory activity only at 100 microM. In the case of LTB(4), WG, WGS and PHF markedly inhibited LTB(4) production at the concentration of 100 microM. We also find that the increase in the IgE content induced by concanavalin A (ConA) was alleviated in the presence WG and WGS, while the inhibitory effect of PHF was much weaker. However, the magnitude of inhibitory effect observed on the content of lipid peroxidation induced by ConA was in order of PHF > WG > WGS, with PHF being the strongest. Interestingly, WG and WGS with the methoxyl group strongly inhibited histamine and IgE production, whereas PHF with the hydroxyl group in the B ring was much stronger than WG and WGS against lipid peroxidation. Based on data, it was concluded that the flavonoid components, WG, WGS, and PHF, may block a common pathway for the release of histamine and LTB(4), and that the IgE level is responsible for the lipid peroxidation induced by ConA.
Copyright 2002 Elsevier Science Ireland Ltd.