Interaction of fatty acids with oxidation of cholesterol and β-sitosterol

The present study studied the effect of stearic acid, oleic acid, linoleic acid and α-linolenic acid on oxidation of cholesterol and β-sitosterol. Both cholesterol and β-sitosterol were instable with 85% of cholesterol and β-sitosterol being degraded at 180 °C for 120 min. Cholesterol and β-sitosterol had a similar degradation pattern and produced 7-keto, 7α-hydroxy, 7β-hydroxy, 5,6α-epoxy and 5,6β-epoxy oxidative derivatives, indicating position 7 was the most susceptible site of oxidation. Four fatty acids accelerated the degradation of cholesterol and β-sitosterol for the first 60 min at 180 °C and thereafter their oxidation-promoting effect became weaker or diminished. When the oxidation progressed to 120 min, cholesterol and β-sitosterol in the presence of α-linolenic acid, was less oxidised when compared with the control, suggesting that it might inhibit the oxidation. It was concluded that the surrounding fatty acids affected sterol oxidation in a time-dependent manner and their effect was unlikely related to their degree of unsaturation.