Abstract
α-Tocopherol, ascorbic acid, catechins ((+)-catechin, (-)-epicatechin, (-)-epigallocatechin, (-)-epicatechin gallate and (-)-epigallocatechin gallate), furanones (2,5 dimethyl-4-hydroxy-3(2H)-furanone and 2-ethyl-4-hydroxy-5-methyl-3(2H)-furanone), pyrogallol, hydroxyhydroquinone and resveratrol donated hydrogen atoms to stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) in a biphasic solvent system. When ascorbic acid, (-)-epicatechin gallate or (-)-epigallocatechin gallate was combined with α-tocopherol, the mixtures donated hydrogen atoms more than those calculated. Most of these water-soluble antioxidants inhibited the formation of thiobarbituric acid-reactive substances in the radical initiator-induced oxidation of methyl linoleate in a homogeneous system. However, the water-soluble antioxidants except for ascorbic acid showed no significant synergistic antioxidant activities when they were combined with α-tocopherol. In this system, ascorbic acid strongly inhibited α-tocopherol decomposition, whereas other water-soluble antioxidants slightly. Interestingly, α-tocopherol slightly inhibited decomposition of most of these water-soluble antioxidants. It is unlikely that water-soluble antioxidants except for ascorbic acid regenerate α-tocopherol and acts as synergists in combination with α-tocopherol.
