In the title compound, C(16)H(15)N(3)O(6), the dihedral angle between the two benzene rings is 0.9 (2)°. The mol-ecule adopts an E configuration with respect to the C=N bond. There are intra-molecular O-H⋯N and O-H⋯O hydrogen bonds in the mol-ecule. In the crystal structure, mol-ecules are linked through inter-molecular N-H⋯O hydrogen bonds to form chains running along the c axis.