We found out 2',3'-dihydroxypuberulin from South American medicinal plant, V. thapsus L., as a candidate of an anti-allergic lead which inhibits the expression of high-affinity receptor of IgE (Fc epsilon RI) on the surface of mast cells. Furthermore, the analysis of structure-activity relationship by using synthesized 2',3'-dihydroxypuberulin analogs revealed that both hydroxy groups in the side chain and both of methyl moieties on phenolic hydroxy groups were crucial for potent activity, but absolute configuration of C-3' position wasn't. The active principle, 2',3'-dihydroxypuberulin, was disclosed to down-regulate the mRNA level of beta-chain of Fc epsilon RI, different from previous reported active natural product reducing.-chain level.