ABSTRACT
Molecules provided with an antioxidant function may have additional properties, the latter being sometimes of more importance than the former. Vitamin A in large doses increased the antioxidant potential of the tissues, and it was suggested that retinol also might be considered as a potential antioxidant similar to tocopherol in animal nutrition. Melatonin as a free radical scavenger that has been implicated in aging and age-related diseases. The inhibitions by a-tocopherol of protein kinase C activity and of proliferation are parallel events in vascular smooth muscle cells. α-Tocopherol hydroquinone is an oxidized product of α-tocopherol and an efficient antioxidant. Melatonin affords protection against gastric lesions induced by ischemia reperfusion possibly due to its antioxidant and mucosal microcirculatory effects. The newly discovered mechanism for the inhibition is unrelated to the antioxidant properties of the α-tocopherol hydroquinone and requires attachment of the active site thiol groups of the carboxylase to one or more methyl groups on vitamin E quinone.
