Two new compounds, (20R)-3α-hydroxy-29-dimethoxylupan-23,28-dioic acid (1) and 3α-hydroxylup-20(29)-ene-23,28-dioic acid 28-O-[β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl] ester (2), and eight known lupane-type triterpenoids (3-10), were isolated from steamed leaves of Acanthopanax koreanum. Chemical structures were determined using a combination of spectroscopic analyses and chemical reactivity. Compounds 1-10 were evaluated for their inhibitory activities on lipopolysaccharide (LPS)-stimulated interleukin (IL)-12 production in bone marrow-derived dendritic cells (BMDCs). Compound 1 exhibited inhibitory activity with IC(50) value of 26.5 μM on IL-12 production, compared with IC(50) value of 29.6 μM for the positive control. Compound 1 also showed significant suppression of LPS-stimulated IL-6 and tumor necrosis factor-alpha (TNF-α) production.