Four ursane-type triterpenoids, 2${alpha}$,3${alpha}$,19${alpha}$-trihydroxy-24-norurs-4(23),12-dien-28-oic acid (1), 4(R),23-epoxy-2${alpha}$,3${alpha}$,19${alpha}$-trihydroxy-24-norurs-12-en-28-oic acid (2), myrianthic acid (3), and tormentic acid (4), and a phenolic compound, ethyl gallate (5), from an EtOAc-soluble extract of the stems of Rumex japonicus, were subjected to in vitro bioassays to evaluate advanced glycation end products (AGEs) and rat lens aldose reductase (RLAR) inhibitory activity. Compounds 1 and 5 exhibited a significant inhibitory activity on AGEs formation with $IC_{50}$ value of 87 ${mu}M$ and on RLAR with $IC_{50}$ value of 14.3 ${mu}M$, respectively. Ethyl gallate (5) was isolated for the first time from this plant.