Phenolic antioxidants in foodstuffs, such as tea polyphenols and flavonoids, inhibited histamine and LTB4 release from rat peritoneal exudate cells. Among them, triphenol compounds suppressed histamine release, but not diphenol compounds. In LTB4 release, most phenolic compounds with 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity exerted an inhibitory effect. Carboxylated phenols, or quercetin glycosides, exerted weak activity, irrespective of their strong radical scavenging activity. This suggests that membrane permeation of phenols is necessary for the inhibition of LTB4 release. In addition, unsaturated fatty acids with more than 3 double bonds significantly suppressed LTB4 release. Feeding experiments suggested that perilla oil, rich in n-3 α-linolenic acid, decreases LTB4-releasing activity of the cells, probably by reducing the proportion of arachidonic acid in membrane phospholipids. Tea polyphenols feeding decreased the activity through some different mechanism.
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