ENZYMATIC DETERMINATION OF CHOLESTEROL OXIDES

For measurement of the concentration of oxidised cholesterols in foods tuffs, a method was developed by adapting the well-known enzymatic det ermination of cholesterol. A linear correlation was found between the absorbance measured after enzymatic reaction and the concentrations of 7 alpha-hydroxycholesterol, 7 beta-hydroxycholesterol, 7-ketocholeste rol, cholesterol-5 alpha, 6 alpha-epoxide in the range 1-12 mu g. The usefulness of this method was demonstrated by determination of the fou r cholesterol oxidation products separated by TLC from the non-saponif iable lipid fraction of 5-month-old whole-egg powder (stored under dif ferent conditions) and of biscuit enriched with egg powder. The main a dvantages of the combination of TLC and the enzymatic method, beyond i ts rapidity and sensitivity, are that the determination of cholesterol oxidation products can be carried out in parallel with many samples c ontaining small amounts of oxidised cholesterols even in the presence of a large quantity of cholesterol.