Isostructurality Among 5 Solvatomorphs of Betulin: X-Ray Structure and Characterization

Abstract

Betulin (BE), a triterpene found in many plant species, has recently attracted the attention of researchers because of its important physiological and pharmacological properties, such as anti-HIV and anticancer activities. Studies have revealed the solvatomorphism of BE (I with dimethyl sulfoxide and III with ethanol, named by author), which means more solvatomorphs may be obtained when different solvents are used during crystallization. After solid-form screening tests, 3 new solvatomorphs of BE with methanol (II), n-propanol (IV), and isopropanol (V) were obtained. In this work, 5 BE solvatomorphs were characterized by X-ray powder diffractometric, thermogravimetric, and Fourier transform infrared spectroscopic analyses. Single-crystal X-ray diffraction was used to analyze the X-ray structures of the compounds, and all 5 solvatomorphs were proven to be isostructral. Change in the crystal symmetry, intermolecular arrangements, stoichiometry, and hydrogen bonding interactions of the solvatomorphs resulted from solvent incorporation to the solvates. Solvatomorphs II, IV, and V, along with their single-crystal structures, were reported for the first time.

Keywords: betulin; crystal structure; isostructurality; solvate; solvatomorphism.