The title octa­deca­trienoic acid derivative, C18H26O4, was isolated from Silene maritima With. (Caryophyllaceae), the first time this natural compound has been found in the Caryophyllales order. This fatty acid has an 18-carbon backbone with three double bonds on trans (E) conformation and two carbonyl. In the crystal, molecules are linked via pairs of O—H⋯O hydrogen bonds, forming inversion dimers.

In the title compound, C11H13NO2, the dihedral angle between the planes defined by the 2-hy­droxy­phenyl­amino group and the pent-3-en-2-one mean plane [maximum deviations = 0.0275 (19) and 0.054 (2) Å, respectively] is 31.01 (10)°. There are intra­molecular bifurcated N—H⋯(O,O) hydrogen bonds involving the amine NH group and the adjacent carbonyl and hy­droxy O atoms. In the crystal, mol­ecules are linked via O—H⋯O hydrogen bonds, forming chains propagating along [100].

In the title compound, C23H19N3O2, the dihedral angles formed by the pyrazolone ring with the three benzene rings are 30.91 (6), 60.96 (4) and 57.01 (4)°. The ligand is in the enamine–keto form and its structure is stabilized by an intra­molecular N—H⋯O hydrogen bond. In the crystal, O—H⋯N hydrogen bonds link mol­ecules into chains parallel to [01-1].