Relaxation mechanisms of chloroform root extracts of Prangos heyniae and Prangos uechtritzii on mouse corpus cavernosum.

Erectile dysfunction (ED) is the inability to achieve/maintain an erection. Because of the side effects, interactions, or ineffectiveness of currently used drugs, novel drug discovery studies are ongoing. The roots of Turkish endemic plants Prangos uechtritzii and Prangos heyniae are traditionally used as aphrodisiacs in Anatolia and contain coumarin-like relaxant compounds. This study aims to reveal the relaxant effect mechanisms of chloroform root extracts of P. heyniae (Ph-CE) and P. uechtritzii (Pu-CE). Isolated organ bath experiments were performed on Swiss albino mouse corpus cavernosum by DMT strip myograph. Relaxant responses to extract (10 -7 -10 -4  g/ml) were obtained in the presence/absence of NO and H 2 S synthesis inhibitors nitro-l-arginine methyl ester (l-NAME, 100 μM) and aminooxyacetic acid (AOAA, 10 mM) respectively. Sodium nitroprusside (SNP, 10 -9 to 10 -4  M) and Na 2 S (10 -6 to 3 × 10 -3  M)-induced relaxations and CaCl 2 (10 -6 to 10 -4  M), KCl (10 -2.1 to 10 -0.9  M) and phenylephrine (3 × 10 -8 to 3 × 10 -5  M)-induced contractions were taken in the presence/absence of the extracts (10 -4  g/ml). Relaxations induced by Ph-CE but not by Pu-CE were inhibited in the presence of l-NAME and AOAA. Ph-CE increased Na 2 S- and SNP-induced relaxations. Ph-CE and Pu-CE decreased the contractions of KCl, phenylephrine, and CaCl 2 . It was concluded that NO and H 2 S synthesis/downstream mechanisms play roles in relaxations of Ph-CE but not in Pu-CE-induced relaxations. Inhibition of calcium influx appears to be involved in the relaxant effect of Ph-CE and Pu-CE. Since the extracts act directly by relaxing smooth muscle or through H 2 S as well as NO, they may be a potential therapeutic agent in diseases such as ED where the bioavailability of NO is impaired.