In Vitro and in Vivo Effects of Fatty Acids and Phenolic Compounds on Chemical Mediator Release from Rat Peritoneal Exudate Cells

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.