[Study on polymorphism of gossypol by infrared spectrophotometry and X-ray diffraction]

The polymorphism of gossypol has been investigated by IR spectrophotometry and X-ray diffraction. Nine samples of gossypol crystallized from mixed solvent of ether, ethanol and water (1:2:2), five samples from chloroform and ten samples from petroleum ether (bp 60-90 degrees C) were determined. Significant differences in the infrared spectra of gossypol crystallized from three solvents were observed near 3500 cm-1. The spectrum of gossypol crystallized from mixed solvent of ether, ethanol and water (mp 183-184 degrees C) showed bands at 3500 (sh), 3470, 3375 cm-1; that from chloroform (mp 198-199 degrees C) at 3455, 3415 (sh) cm-1 and that from petroleum ether (mp 213-214 degrees C) at 3510, 3495, 3430 (sh), 3410 cm-1. Moreover, the spectra of the three forms of gossypol showed slightly different bands at 780 and 600-400 cm-1. Gossypol crystallized from the three solvents showed the same infrared spectra after being crystallized from acetone. Significant differences in the X-ray diffraction pattern of gossypol crystallized from the three solvents were also observed. Angles, intensities and D-values of most of the X-ray diffraction peaks were listed.