Semen cassiae Extract Inhibits Contraction of Airway Smooth Muscle

β -adrenoceptor agonists are commonly used as bronchodilators to treat obstructive lung diseases such as asthma and chronic obstructive pulmonary disease (COPD), however, they induce severe side effects. Therefore, developing new bronchodilators is essential. Herbal plants were extracted and the extracts' effect on airway smooth muscle (ASM) precontraction was assessed. The ethyl alcohol extract of (EESC) was extracted from . The effects of EESC on the ACh- and 80 mM K -induced sustained precontraction in mouse and human ASM were evaluated. Ca permeant ion channel currents and intracellular Ca concentration were measured. HPLC analysis was employed to determine which compound was responsible for the EESC-induced relaxation. The EESC reversibly inhibited the ACh- and 80 mM K -induced precontraction. The sustained precontraction depends on Ca influx, and it was mediated by voltage-dependent L-type Ca channels (LVDCCs), store-operated channels (SOCs), TRPC3/STIM/Orai channels. These channels were inhibited by , one component of EESC. When removed, EESC's action disappeared. In addition, inhibited the precontraction of mouse and human ASM and intracellular Ca increases. These results indicate that -contained inhibits sustained precontraction of ASM via inhibiting Ca -permeant ion channels, thereby, which could be used to develop new bronchodilators.