Crystal structures of fisetin dihydrate and luteolin monohydrate: crystallization from ethanol-water mixtures

The crystal structures of two hydrates of aglycon flavonoids, fisetin dihydrate [systematic name: 2-(3,4-di-hydroxy-phen-yl)-3,7-dihy-droxy-4H-1-benzo-pyran-4-one dihydrate, C₁₅H₁₀O₆·2H₂O, P2₁, Z = 2] and luteolin monohydrate [systematic name: 2-(3,4-di-hydroxy-phen-yl)-3,7-dihy-droxy-4H-1-benzo-pyran-4-one monohydrate, C₁₅H₁₀O₆·H₂O, P4₁2₁2, Z = 8] were determined by single-crystal X-ray diffraction (SCXRD) and are reported for the first time. The two crystal forms were obtained from ethanol-water mixtures. These structures provide a foundation for future studies on the thermodynamic role of water mol-ecules in crystal stability and packing, enabling further investigation of hydration effects on flavonoid solubility and stability.