(−)-Epigallocatechin gallate inhibits Mos activation-mediated Xenopus oocyte maturation induced by progesterone

(−)-Epigallocatechin gallate (EGCG), one of the constituents of green tea known to have a tumor preventing effect, inhibited maturation of Xenopus laevis oocytes induced by progesterone when this polyphenol was microinjected into oocytes at a final concentration of about 1 mM. Western blot and activity measurement analyses showed that Mos translation and the subsequent activations of mitogen-activated protein kinase and p90rsk, probably by protein phosphorylation, seemed to have been inhibited by the microinjection of EGCG. These results suggest that EGCG may have the ability to control Xenopus oocyte maturation at least during the stage of Mos activation.