Effects of adlay hull extracts on uterine contraction and Ca²⁺ mobilization in the rat

Dysmenorrhea is directly related to elevated PGF^2α levels. It is treated with nonsteroid antiinflammatory drugs (NSAIDs) in Western medicine. Since NSAIDs produce many side effects, Chinese medicinal therapy is considered as a feasible alternative medicine. Adlay (Coix lachryma-jobi L. var. ma-yuen Stapf.) has been used as a traditional Chinese medicine for treating dysmenorrhea. However, the relationship between smooth muscle contraction and adlay extracts remains veiled. Therefore, we investigated this relationship in the rat uterus by measuring uterine contraction activity and recording the intrauterine pressure. We studied the in vivo and in vitro effects of the methanolic extracts of adlay hull (AHM) on uterine smooth muscle contraction. The extracts were fractionated using four different solvents: water, 1-butanol, ethyl acetate, and n-hexane; the four respective fractions were AHM-Wa, AHM-Bu, AHM-EA, and AHM-Hex. AHM-EA and its subfractions (175 μg/ml) inhibited uterine contractions induced by PGF_2α, the Ca²⁺ channel activator Bay K 8644, and high K⁺ in a concentration- dependent manner in vitro. AHM-EA also inhibited PGF_2α-induced uterine contractions in vivo; furthermore, 375 μg/ml of AHM-EA inhibited the Ca²⁺-dependent uterine contractions. Thus 375 μg/ml of AHM-EA consistently suppressed the increases in intracellular Ca²⁺ concentrations induced by PGF_2α and high K⁺. We also demonstrated that naringenin and quercetin are the major pure chemical components of AHM-EA that inhibit PGF_2α-induced uterine contractions. Thus AHM-EA probably inhibited uterine contraction by blocking external Ca²⁺ influx, leading to a decrease in intracellular Ca ²⁺ concentration. Thus adlay hull may be considered as a feasible alternative therapeutic agent for dysmenorrhea.