Regeneration of alpha-tocopherol in human low-density lipoprotein by green tea catechin.
Oxidative modification of low-density lipoproteins (LDL) may play an important role in the development of atherosclerosis. alpha-Tocopherol functions as a major antioxidant in human LDL. The present study was to test whether green tea catechins (GTC) would protect or regenerate alpha-tocopherol in human LDL. The oxidation of LDL incubated in sodium phosphate buffer (pH 7.4, 10 mM) was initiated by addition of 1.0 mM of 2,2'-azobis(2-amidinopropane) dihydrochloride at 40 degrees C. It was found that alpha-tocopherol was completely depleted within 1 h. Under the same experimental conditions, the longjing GTC extracts demonstrated a dose-dependent protective activity to alpha-tocopherol in LDL at concentrations ranging from 2 to 20 microM. Four pure epicatechin derivatives showed varying protective activity against depletion of alpha-tocopherol in LDL with (-)-epigallocatechin (EGC) and (-)-epigallocatechin gallate (EGCG) being less effective than (-)-epicatechin (EC) and (-)-epicatechin gallate (ECG). The results showed that addition of longjing GTC extracts, EC, ECG, and EGCG at 5, 10, and 15 min to the incubation mixture demonstrated a gradual regeneration of alpha-tocopherol in human LDL.
Zhu
Q Y
QY
Departments of Biochemistry and Physiology, The Chinese University of Hong Kong, Shatin, Hong Kong.
Huang
Y
Y
Tsang
D
D
Chen
Z Y
ZY
D000578:Amidines / Q000494:pharmacology; D002392:Catechin / Q000031:analogs & derivatives / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D008077:Lipoproteins, LDL / Q000097:blood* / Q000737:chemistry*; D016877:Oxidants / Q000494:pharmacology; D013662:Tea; D014810:Vitamin E / Q000097:blood*
D000578:Amidines; D005419:Flavonoids; D008077:Lipoproteins, LDL; D016877:Oxidants; D013662:Tea; D014810:Vitamin E; C046728:2,2'-azobis(2-amidinopropane); D002392:Catechin; C045651:epigallocatechin gallate; C057580:gallocatechol