Embelin, a major constituent of Embelia ribes BURM. (Myrsinaceae) was transformed into different types of compounds through dimerization during preparation of a decoction. Two of the products are proposed to have furanylidene benzofuranone and 1, 4-dibenzofurandione skeletons on the basis of spectroscopic means. The transformation of embelin in boiling water is markedly accelerated by the presence of fatty acids.