Thermal analysis and microscopical characterization of cholesterol in gallstones

Cholesterol constitutes the major component of most gallstones. It was identified and determined in gallstones by thermal analysis technique (DSC and TG-DTA), mainly by the use of the melting temperature (Tonset=145 deg C and Tmax=149 deg C) and by DTG peak decomposition (Tmax=364 deg C). Cholesterol anhydrous (ChA), which showed endothermic polymorphic peak, Tmax=40 deg C, without mass loss, was differentiated from cholesterol monohydrate (ChH), which showed a broad endothermic peak, Tmax=59 deg C, attributed to loss of water of crystallization (theoretical 4.45%). Morphological studies of gallstones were performed by optical microscopy and scanning electron microscopy (SEM). The stones consisted of a pigmented core with a variably-sized irregular central cavity, surrounded by a radially arranged deposits of plate-like ChH. The outer part of the stones showed ChA crystal arborescences. X-ray microanalysis gave a typical spectrum rich in C and O, and in some instances the presence of P, which was attributed to the presence of phospholipids. CaCO3 was easily characterized by TG with the use of DTG decomposition peak at 674 deg C.