Analysis of Four Solvatomorphs of Betulin by TG-DTA-EI/PI-MS System Equipped with the Skimmer-Type Interface

Betulin(BE)has exceedingly become a potential natural product,providing multiple pharmacological and biological activi-ties,including anti-cancer,anti-viral,and anti-inflammatory benefits.Previous research indicated that the solvatomorphism of BE can easily occur through crystallization with different organic solvents.This property of BE can directly affect its extraction,isolation,and preparation process.In this study,a system of thermogravimetry(TG)-differential thermal analysis(DTA)coupled with mass spectrometry(MS)with electron ionization(EI)and photoionization(PI)capability,equipped with the skimmer-type interface(i.e.,skimmer-type interfaced TG-DTA-EI/PI-MS system),as a real-time and onsite analysis technique,was employed.Then,four solvatomorphs of BE,namely,with pyridine and water(A),sec-butanol(B),n,n-dimethylformamide(DMF)(C),and isopropanol(V),were analyzed for the first time.Finally,five kinds of the main volatile gaseous species,including H2O,pyridine,sec-butanol,DMF,and isopropanol,were identified clearly.Furthermore,the multi-step desolvation processes of the four solvatomorphs of BE were revealed by this system for the first time.This system showed great potential for the rapid and accurate analysis of various solvatomorphs of natural products.

Study on four polymorphs of bifendate based on X-ray crystallography

Bifendate, a synthetic anti-hepatitis drug, exhibits polycrystalline mode phenomena with 2polymorphs reported(forms A and B). Single crystals of the known crystalline form B and 3 new crystallosolvates involving bifendate solvated with tetrahydrofuran(C), dioxane(D), and pyridine(E) in a stoichiometric ratio of 1:1 were obtained and characterized by X-ray crystallography, thermal analysis,and Fourier transform infrared(FT-IR) spectroscopy. The differences in molecular conformation,intermolecular interaction and crystal packing arrangement for the four polymorphs were determined and the basis for the polymorphisms was investigated. The rotation of single bonds resulted in different orientations for the biphenyl, methyl ester and methoxyl groups. All guest solvent molecules interacted with the host molecule via an interesting intercalative mode along the [1 0 0] direction in the channel formed by the host molecules through weak aromatic stacking interactions or non-classical hydrogen bonds, of which the volume and planarity played an important role in the intercalation of the host with the guest. The incorporation of solvent-augmented rotation of the C–C bond of the biphenyl group had a striking effect on the host molecular conformation and contributed to the formation of bifendate polymorphs. Moreover, the simulated powder X-ray diffraction(PXRD) patterns for each form were calculated on the basis of the single-crystal data and proved to be unique. The single-crystal structures of the four crystalline forms are reported in this paper.