Regeneration of alpha-tocopherol in human low-density lipoprotein by greentea catechin

Oxidative modification of low-density lipoproteins(LDL) may play an importa nt role in the development of atherosclerosis. alpha-Tocopherol functions a s a major antioxidant in human LDL. The present study was to test whether g reen tea catechins (GTC) would protect or regenerate alpha-tocopherol in hu man 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 c ompletely 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 mu M. Four p ure epicatechin derivatives showed varying protective activity against depl etion of alpha-tocopherol in LDL with (-)-epigalloeatechin (EGC) and (-)-ep igallocatechin gallate (EGCG) being less effective than (-)-epicatechin (EC ) and (-)-epicatechin gallate (ECG). The results showed that addition of lo ngjing GTC extracts, EC, EGG, and EGCG at 5, 10, and 15 min to the incubati on mixture demonstrated a gradual regeneration of alpha-tocopherol in human LDL.