Two new resin glycosides, operculin I and II, were isolated from the ether-soluble fraction ("jalapin")[W. Mayer, Justus Libigs Ann. Chem., 83, 121 (1852)] of Rhizoma Jalapae braziliensis, the root of Ipomoea operculata (Convolvulaceae), and their structures have been determined. Both compounds provided on alkaline hydrolysis one identical jalapinolic acid 11-0-glycoside, named operculinic acid A, which forms and intramolecular macrocyclic ester in the parent compounds similarly to the case of analogs isolated from "jalapin" of all the Convolvulaceae plants so far examined. It is noted, however, that operculin I and II have two moles of a fatty acid, n__--dodecanoic and n__--decanoic acids, respectively, combined at their sugar moiety in place of several organic acids. Accordig to Mosher's method, the absolute configuration at C₁₁ of methyl jalapinolate, which was regarded by Horeau's method as R__-, was shown to be S__-.