Structure-activity relationship of polyphenols on inhibition of chemical mediator release from rat peritoneal exudate cells

The effect of phenolic compounds in foodstuffs on histamine and leukotriene B-4 (LTB4) release from rat peritoneal exudate cells and their antioxidati ve activity were examined to assess their antiallergenic activities. Among them, triphenols such as pyrogallol and gallic acid inhibited histamine rel ease from the cells, but diphenols did not. On the other hand, o- and p-dip henols such as catechol and hydroquinone with strong antioxidative activity inhibited LTB4 release as strongly as pyrogallol, but an m-derivative reso rcinol with weak antioxidative activity did not. Though carboxylated compou nds and their noncarboxylated counterparts were antioxidative, the former e xerted a much weaker inhibitory effect on the LTB4 release than the latter. In flavonols, only myricetin with a triphenolic B ring strongly inhibited histamine release, but all flavonols strongly suppressed LTB4 release irres pective of the number of OH groups in the B ring. Among flavonoids with an o-diphenolic B ring, flavonol and flavone with a C-4-carbonyl group strongl y inhibited LTB4 release, whereas the activity of anthocyan without C-4-car bonyl was much weaker than the above compounds. These results suggest that triphenolic structure is essential for the inhibition of histamine release. On the other hand, antioxidative activity and membrane permeability of phe nolic compounds seemed to be essential for the inhibition of LTB4 release. In addition, the C-4-carbonyl group seemed to be important for strongly inh ibiting LTB4 release.