Conclusion: Cnidium Monnieri (Shi Chuang Zi) naturally increases nitric oxide release, which powerfully increases the production of cGMP. Cyclic Guanosine Monophosphate (cGMP) is the key in obtaining and sustaining a powerful erection. cGMP relaxes the muscles around the penis, which makes it possible for the cells in the penis to take in blood, thus allows you to experience a proper erection.

Chen J, Chiou WF, Chen CC, Chen CF. Institute of Clinical Medicine, National Yang-Ming University, and National Research Institute of Chinese Medicine, Taipei, Taiwan, Republic of China.

PURPOSE: We investigated the cavernosal relaxant effect of osthole, a coumarin isolated from Cnidium monnier (L.) Cusson which has been long used in China as a herbal medicine to improve male sexual dysfunction. MATERIALS AND METHODS: Strips of rabbit corpus cavernosum were precontracted with phenylephrine. Corporal relaxation evoked by osthole was then determined in the absence and presence of nitric oxide synthase inhibitor (L-NAME), soluble guanylate cyclase inhibitor (ODQ), cyclooxygenase inhibitor (indomethacin), tetradotoxin, and after endothelium deprivation. RESULTS: Corpus cavernosal strips showed relaxation in response to osthole (0.1 approximately 30 microM) in a dose-dependent manner. These effects were reduced partially but significantly by pretreatment with L-NAME, ODQ and by endothelial disruption. However, they were not affected by indomethacin and tetradotoxin treatment. Osthole pretreatment (from 1 to 30 microM) enhanced the sodium nitroprusside (0.3 microM)-induced relaxation of corpus cavernosum in a dose-dependent manner to a maximum of 3 times the pretreatment level at 30 microM osthole. However, this effect was abolished in the presence of zaprinast. Additionally, a higher concentration of osthole (30 microM) also enhanced forskolin-induced relaxation. CONCLUSION: The data suggested that osthole possesses a relaxant effect on rabbit corpus cavernosal tissues which is attributable to the release of NO from sinusoidal endothelium and to the potentiation of the cGMP and/or cAMP signal mediating relaxation of cavernosal smooth muscle by inhibiting phosphodiesterase.