title: Physical changes of beta-sitosterol crystals in oily suspensions during heating.
abstract: The aim of this research was to describe the thermal behavior of beta-sitosterol crystals in oil-suspensions with a focus on the role of water during heating. The suspensions were prepared by recrystallization in order to achieve a microcrystalline particle size. The structural changes together with the mechanical properties of the suspensions during heating were studied by using variable temperature X-ray powder diffractometry (VT-XRPD), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). Hydrated beta-sitosterol crystals in an oil-suspension dehydrated, despite the composition of the suspensions, at low temperatures. At high beta-sitosterol concentration, the monohydrate crystal form changed partially to a hemihydrated form, and when only a small amount of water was initially incorporated, the hemihydrate crystal form dehydrated to a mostly anhydrate crystal form. The released water, which was immiscible in the surrounding oil, caused the recrystallization of hydrated beta-sitosterol during cooling. This procedure indicated a reversible dehydration process. Structural and thermal analysis of beta-sitosterol crystals in suspensions, together with mechanical analysis made it possible to understand various physical changes during heating.
authors.affiliation: Division of Pharmaceutical Technology, Faculty of Pharmacy, University of Helsinki. anna.vonbonsdorff@helsinki.fi
authors.forename: Anna
authors.initials: A
authors.lastname: von Bonsdorff-Nikander
authors.forename: Satu
authors.initials: S
authors.lastname: Lievonen
authors.forename: Leena
authors.initials: L
authors.lastname: Christiansen
authors.forename: Milja
authors.initials: M
authors.lastname: Karjalainen
authors.forename: Jukka
authors.initials: J
authors.lastname: Rantanen
authors.forename: Jouko
authors.initials: J
authors.lastname: Yliruusi
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003460:Crystallization; D006358:Hot Temperature; D009821:Oils / Q000032:analysis / Q000737:chemistry*; D012855:Sitosterols / Q000032:analysis / Q000737:chemistry*; D013535:Suspensions / Q000032:analysis / Q000737:chemistry
chemical_list: D009821:Oils; D012855:Sitosterols; D013535:Suspensions; C025473:gamma-sitosterol