Oxidation of cholesterol and beta-sitosterol and prevention by natural antioxidants.
Consumption of cholesterol oxidation products (COPs) is a growing health concern, but little is known about the intake of beta-sitosterol oxidation products (SOPs). The present study was performed (i) to compare the oxidative stability of cholesterol with that of beta-sitosterol; (ii) to investigate the oxidative pattern of cholesterol and beta-sitosterol in lard, corn oil, and olive oil; and (iii) to examine the effectiveness of green tea catechins (GTC), alpha-tocopherol, and quercetin in prevention of cholesterol and beta-sitosterol oxidation compared with butylated hydroxytoluene (BHT). Results showed both cholesterol and beta-sitosterol were thermally unstable with 75% of cholesterol and beta-sitosterol being oxidized at 180 degrees C for 2 h. The oxidation behavior of beta-sitosterol was similar to that of cholesterol in terms of oxidative rate and oxidation products. The major COPs produced were 7-ketocholesterol, 7alpha-hydroxycholesterol, 7beta-hydroxycholesterol 5,6alpha-epoxycholesterol, and 5,6beta-epoxycholesterol, whereas the major SOPs were 7-ketositosterol, 7alpha-hydroxysitosterol, 7beta-hydroxysitosterol, 5,6alpha-epoxysitosterol, and 5,6beta-epoxysitosterol. Under the same experimental conditions, both cholesterol and beta-sitosterol were oxidized more slowly in corn oil, lard, and olive oil, attributable to the unsaponified antioxidants present in these fat and oils. GTC, alpha-tocopherol, and quercetin were more effective than BHT in preventing the oxidation of cholesterol and beta-sitosterol.
Xu
Guihua
G
Department of Biochemistry, Faculty of Science, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, China.
Guan
Lei
L
Sun
Junliang
J
Chen
Zhen-Yu
ZY
D000975:Antioxidants / Q000494:pharmacology*; D002084:Butylated Hydroxytoluene / Q000494:pharmacology; D002784:Cholesterol / Q000737:chemistry*; D002849:Chromatography, Gas; D003314:Corn Oil / Q000737:chemistry; D004041:Dietary Fats / Q000032:analysis; D004355:Drug Stability; D007700:Kinetics; D000069463:Olive Oil; D010084:Oxidation-Reduction; D010938:Plant Oils / Q000737:chemistry; D011794:Quercetin / Q000494:pharmacology; D012855:Sitosterols / Q000737:chemistry*; D013662:Tea / Q000737:chemistry; D024502:alpha-Tocopherol / Q000494:pharmacology
D000975:Antioxidants; D004041:Dietary Fats; D000069463:Olive Oil; D010938:Plant Oils; D012855:Sitosterols; D013662:Tea; D002084:Butylated Hydroxytoluene; C025473:gamma-sitosterol; D003314:Corn Oil; D002784:Cholesterol; D011794:Quercetin; D024502:alpha-Tocopherol; C029310:lard