SCREENING FOR INHIBITORY ACTIVITY OF CITRUS-FRUIT EXTRACTS AGAINST PLATELET CYCLOOXYGENASE AND LIPOXYGENASE

Inhibitory activities of the albedo extracts of 42 species and cultiva rs of the genus Citrus and those of two Fortunella and one Poncirus sp ecies against rat platelet cyclooxygenase and lipoxygenase were screen ed. Among the species investigated, the extract of Lumie (Citrus lumia ) was shown to possess the highest inhibitory activity against cycloox ygenase (IC50 = 24 mu g/mL), and that of Shuto (Citrus aurantium) was the highest against lipoxygenase (IC50 = 56 mu g/mL). The albedo extra cts of citrus from the same taxonomic group appeared to have similar i nhibitory tendencies toward these enzymes. The flavedo extract of ripe lumie inhibited cyclooxygenase to the same degree as the albedo, more than the pulp extract. The flavedo, pulp, and juice extracts of ripe Ponkan (C. reticulata) also inhibited lipoxygenase in addition to the albedo extract. Both the flavedo and albedo tissues were shown to be e ffective sources of inhibitory compounds against cyclooxygenase and li poxygenase.