Effects of eupatilin on the contractility of corpus cavernosal smooth muscle through nitric oxide‐independent pathways

Summary Eupatilin (5,7‐dihydroxy‐3,4,6‐trimethoxyflavone) is one of the main compounds present in Artemisia species. Eupatilin has both antioxidative and anti‐inflammatory properties and a relaxation effect on vascular contraction regardless of endothelial function. We evaluated the relaxant effects of eupatilin on the corpus cavernosum (CC) of rabbits and the underlying mechanisms of its activity in human corpus cavernosum smooth muscle (CCSM) cells. Isolated rabbit CC strips were mounted in an organ bath system. A conventional whole‐cell patch clamp technique was used to measure activation of calcium‐sensitive K+‐channel currents in human CCSM cells. The relaxation effect of eupatilin was evaluated by cumulative addition (10−5 m ~ 3 × 10−4 m) to CC strips precontracted with 10−5 m phenylephrine. Western blotting analysis was performed to measure myosin phosphatase targeting subunit 1 (MYPT1) and protein kinase C‐potentiated inhibitory protein for heterotrimeric myosin light chain phosphatase of 17‐kDa (CPI‐17) expression and to evaluate the effect of eupatilin on the RhoA/Rho‐kinase pathway. Eupatilin effectively relaxed the phenylephrine‐induced tone in the rabbit CC strips in a concentration‐dependent manner with an estimated EC50 value of 1.2 ± 1.6 × 10−4 m (n = 8, p