INHIBITORY EFFECTS OF APPLE POLYPHENOL ON INDUCED HISTAMINE-RELEASE FROM RBL-2H3 CELLS AND RAT MAST-CELLS

The anti-allergic activities of polyphenol fractions extracted from im mature fruits of apple (Rosaceae, Malus sp.) were evaluated by in vitr o assays. A crude apple polyphenol (CAP) fraction, which had been obta ined from the juice of immature apples by reverse-phase column chromat ography, was further purified by LH-20 column chromatography to obtain an apple condensed tannin (ACT) fraction consisting of linear oligome ric epicatechins from the dimer to pentadecamer. ACT strongly inhibite d the release of histamine from rat basophilic leukemia (RBL-2H3) cell s stimulated by the antigen-stimulation and from rat peritoneal mast c ells stimulated by compound 48/80. The IC50 values for histamine relea se were 30 mu g/ml and 25 mu g/ml, respectively. ACT also inhibited hy aluronidase activity and the increase in intracellular free calcium co ncentration in RBL-2H3 cells stimulated with the antigen. These result s suggest that ACT affected early signal transduction including the ca lcium influx.