A new oleanene glucuronide called melilotus-saponin O₁ (1) was isolated together with three known ones from the roots of Melilotus officinalis (L.) PALLAS (Leguminosae). The structure of 1 was determined to be 3-O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl-(1→3)]-β-D-galactopyranosyl-(1→2)-β-D-glucuronopyranosyl soyasapogenol B by spectroscopic and chemical methods.