Antioxidant activity of green tea polyphenols against lipid peroxidation initiated by lipid-soluble radicals in micelles

摘要

Antioxidant effects of the principal polyphenolic components extracted from green tea leaves, i.e., (u0002)-epicatechinn(EC), (u0002)-epicatechin gallate (ECG), (u0002)-epigallocatechin (EGC) and (u0002)-epigallocatechin gallate (EGCG), againstnperoxidation of linoleic acid have been studied in sodium dodecyl sulfate (SDS) and cetyltrimethylammoniumnbromide (CTAB) micelles. The peroxidation was initiated thermally by a lipid-soluble azo initiator di-tert-butylnhyponitrite (DBHN) and the reaction kinetics were followed by formation of linoleic acid hydroperoxides andnconsumption of the antioxidant. Kinetic analysis of the antioxidation process demonstrates that these green teanpolyphenols are effective antioxidants in micelles used either alone or in combination with α-tocopherol (vitamin E),nbut their antioxidative behaviour and relative effectiveness are substantially different from those in the water-solubleninitiator AMPAD-initiated peroxidations reported previously. The antioxidative action of the green tea polyphenolsn(GOHs) in DBHN-initiated peroxidation involves trapping the initiating tert-butoxyl radical and the propagatingnlinoleic acid peroxyl radicals. However, the GOHs could not participate in the α-tocopherol recycling reaction as innthe case of AMPAD-initiated reactions due to their very fast reaction with the initiating tert-butoxyl radical.