Autoxidation of cholesterol in aqueous dispersions and in monomolecular films

The autoxidative formation of 7-ketocholesterol and diols from aqueous cholesterol dispersions and from cholesterol monomolecular films has been studied as a function of time. The rate of oxidation of cholesterol is much faster at the surface than in the bulk. Whereas more than one-half of the cholesterol is oxidized at the surface within 8 hr at room temperature, no noticeable reaction was observed for the oxidation of cholesterol from aqueous dispersions at room temperature during this time period. However, similar rates of oxidation were observed when the dispersions were maintained at 85 degrees C.