Crystal transformation of a flavonoid derivative DA-6034

DA-6034 is a synthetic flavonoid known to possess anti-inflammatory activity. DA-6034 has been found to exist in six crystal forms, one hydrate form and five solvates. Six crystal forms, one hydrate form and five solvates, of DA-6034 were prepared by recrystallization and they were characterized by DSC, TG and PXRD (Shin and Sohn, J Therm Anal Calorim 115:2457–2461, 2014). This research aimed at investigating the transformation of crystal forms of DA-6034 depending on temperature and relative humidity. Six crystal forms of DA-6034 were kept in different conditions: in 0, 52, and 95 % RH at room temperature to investigate the effect of relative humidity and at RT, 40, and 60 °C to investigate that of temperature. PXRD and TG were used to examine the state of modifications. At 0 % RH Form 2, Form 3, and Form 5 were transformed to amorphous solid and Form 6 was not transformed and Form 4 was transformed to anhydrate. At 52, 95 % RH Form 2, Form 3, Form 4, and Form 6 were transformed to Form 1 (monohydrate) and Form 5 (1.5 H2O, 1/2 acetic acid solvate) was transformed to Form 8 (2 H2O, 0.15 acetic acid solvate).