Sb. Lotito et Cg. Fraga, Catechins delay lipid oxidation and alpha-tocopherol and beta-carotene depletion following ascorbate depletion in human plasma, P SOC EXP M, 225(1), 2000, pp. 32-38
Citations number
39
Categorie Soggetti
Medical Research General Topics
Journal title
PROCEEDINGS OF THE SOCIETY FOR EXPERIMENTAL BIOLOGY AND MEDICINE
Blood plasma was incubated with 50 mM AAPH [2,2'-azobis-(2-amidinopropane)
hydrochloride] in the absence or presence of catechins (5-100 mu M). Lipid
oxidation was evaluated by measuring the formation of 2-thiobarbituric acid
reactive substances (TBARS). The concentration of alpha-tocopherol (AT), b
eta-carotene (BC), ascorbic acid (AA), and catechins was determined by reve
rse phase high performance liquid chromatography (HPLC) with electrochemica
l detection. All the assayed catechins inhibited plasma TBARS formation. Ba
sed on the calculated IC50, the order of effectiveness was: epicatechin gal
late (ECG) > epigallocatechin gallate (EGCG) > epigallocatechin (EGC) > epi
catechin (EC) > catechin (C). Catechins protected plasma AT and BC from AAP
H-mediated oxidation. The order of effectiveness for AT protection was ECG
> EGCG > EC = C > EGG; and for BC protection, the order was EGCG > ECG > EG
C > > EC > C. The addition of catechins modified the kinetics of TEARS form
ation and AT depletion, but the rate of AA depletion was not affected. Cate
chin oxidation did not start until the complete depletion of AA, and it pre
ceded AT depletion. These results indicate that catechins are effective ant
ioxidants in human blood plasma, delaying the lipid oxidation and depletion
of endogenous lipid-soluble antioxidants (AT and BC).