The title compound, C21H22O4, also known as cajanine, features an intra-molecular O-H⋯O hydrogen bond between the adjacent carb-oxy and hy-droxy groups. The benzene rings make an inter-planar angle of 175.4 (2)°. In the crystal, mol-ecules are linked by pairs of O-H⋯O hydrogen bonds, forming inversion dimers.