Effects of chalcones isolated from licorice roots on leukotriene biosynthesis in human polymorphonuclear neutrophls

The effects of chalcones and flavanones isolated from Sinkiang Licorice (Glycyrrhiza inflata Bat.) on leukotriene B4(LTB4) and C4(LTC4) formation in human polymorphonuclear neutrophils (PMNs) were investigated. Licochalcone A (2-methoxy-4,4′-dihydroxy-5-α,α-dimethyl-allylchalcone) and licochalcone B (2-methoxy-3,4,4′-trihydroxychalcone), at concentrations of 10−3 to 10−6 M, inhibited calcium ionophore A 23187 (A 23187)-induced LTB4 and LTC4 formation in human PMNs. The concentration of licochalcones A required for 50% inhibition (LC50) of LTB4 and LTC4 formation was 4.6 × 10−7 and 4.2×10−6 M, respectively, using 2 μM A 23187. The IC50 values of licochalcone B for LTB4 and LTC4 formation were also 1.2 × 10−6 and 2.0×10−6 M, respectively. In addition, licochalcones A and B significantly increased cyclic AMP level in human PMNs at concentrations of 10−4 to 10−3 M. Licochalcones A and B were found to reduce the elevation of the cytosolic free calcium concentration induced by calcium ionomycine, dose-dependently, in the presence of 1 mM Ca2+ or 1 mM EGTA.