Investigation on separations of cholesterol stereoisomers by chromatographic methods and comparision of stereochemical structures of cholesterol from different sources

INVESTIGATION ON SEPARATIONS OF CHOLESTEROL STEREOISOMERS BY CHROMATOGRAPHIC METHODS AND COMPARISON OF STEREOCHEMICAL STRUCTURES OF CHOLESTEROL FROM DIFFERENT SOURCESABSTRACTAs a constituent of cell membrane and a substrate for bile acids and steroid hormone synthesis, cholesterol, which is a lipid, is of great importance. Cholesterol posseses cyclopentanoperhydrophenanthrene structure and has a 256 possible stereoisomer due to the occurence of 8 asymetric carbon atoms. Different stereoisomers bring about different responses in the body. There are a few researches present with respect to metabolism of various cholesterol stereoisomer.Human body takes up cholesterol from various dietary sources. Identification of cholesterol stereoisomers can point out the dietary sources of cholesterol. To this end, stereoisomer analysis of cholesterol from sheep wool and pork liver were conducted by reverse phase HPLC, reverse phase HPLC with modified mobile phase by cyclodextrins as a chiral agents, and HPLC with chiral columns.Stereoisomer analysis of cholesterol from both sources by HPLC with modified mobile phase by cyclodextrins (except for gama cyclodextrin) resulted in two extra peaks other than cholesterol peak, whereas with the other analysis no extra fractions were seen. It is possible therefore that these extra fractions might be stereoisomer of cholesterol or different sterol or chemically modified cholesterol (e.g. oxidized cholesterol).With HPLC analysis by modified mobile phase in pork liver cholesterol samples, extra peak eluted before cholesterol peak was much higher than that in sheep wool cholesterol samples. This result might indicate that stereoisomer composition of cholesterol from different sources might be different.The present results show that steroisomer composition of cholesterol from various sources could be heterogenous. Identification of these structures requires further advanced molecular analysis.Key words: Cholesterol, Stereoisomer, Chromatography, Separation