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 B 4 (LTB 4 ) and C 4 (LTC 4 ) 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 LTB 4 and LTC 4 formation in human PMNs. The concentration of licochalcones A required for 50% inhibition (LC 50 ) of LTB 4 and LTC 4 formation was 4.6 × 10 −7 and 4.2×10 −6 M, respectively, using 2 μM A 23187. The IC 50 values of licochalcone B for LTB 4 and LTC 4 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 Ca 2+ or 1 mM EGTA.