Demethylnobiletin (5-Demethylnobiletin) is a unique flavonoid found in citrus fruits with potential chemopreventive effects against human cancers.5-Demethylnobiletin is a direct inhibitor of 5-LOX with IC50 of 0.1 μM, without affecting the expression of COX-2. 5-Demethylnobiletin has anti-inflammatory activity, inhibits leukotriene B 4(LTB4) formation in rat neutrophils and elastase release in human neutrophils with IC50 of 0.35 μM.