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

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Abstract
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.