THE PAPER CHROMATOGRAPHIC FRACTIONATION OF PLANT STERYL ESTERS

Abstract

The even-numbered C2–C22saturated and the C18-unsaturated fatty acid esters of beta- and gamma-sitosterol, stiginasterol, ergosterol, stigmastanol, and gamma-sitostanol were used separately and in model mixtures for the evaluation of existing and the development of new paper chromatographic methods for the separation and identification of these compounds. Satisfactory separations of the esters were obtained by the ascending reversed phase chromatography on cellulose or glass fiber paper using one of the following systems depending upon the number of carbon atoms in the fatty acid moiety of the ester: C2–C12, aqueous acetic acid/chloroform/paraffin oil; C8–C18, aqueous propionic acid/paraffin oil; C8–C22, acidified aqueous methanol/chloroform/paraffin oil or aqueous butyric acid/paraffin oil. The rate of migration of the esters was inversely proportional to the molecular weight and was increased by the introduction of unsaturation.The increased movement due to unsaturation has been correlated with the number of ethylenic hydrogens, and the possibility that polarity of these atoms might account for this phenomenon is discussed. The reversed phase paper partition chromatography of sterols as their esters is suggested as a potential tool for evaluation of polarity of the various attributes of the sterol nucleus in terms of the chain length of the ester fatty acid. The rule of independent contributions of the constituents of a molecule to its distribution isotherm was observed not to hold in this fatty ester series.