Synthesis and antitussive evaluation of verticinone-cholic acid salt, a novel and potential cough therapeutic agent

Aim: To seek a novel and potent antitussive drug based on Shedan-Chuanbei powder, a complex of traditional Chinese medicine preparation for cough therapy. Methods: Verticinone-cholic acid (Ver-CA) salt, a novel, salifying derivative of verticinone and cholic acid, both of which are the major bioactive components in Shedan-Chuanbei powder, was synthesized. We then evaluated the antitussive activity and the acute toxicity of the salt. Results: The new compound, with good solubility in water, has much more potent antitussive activity in comparison with the same dose of single verticinone and single cholic acid. The administration 3 mg/kg of Ver-CA could result in over 50% reduction of a citric acid-induced cough. Pretreatment with naloxone (0.8 mg/kg, ip) can only partially antagonize its anti-tussive effect. On the other hand, glybenclamide (3 mg/kg, ip), an ATP-sensitive K+ channel blocker, can also significantly reduce the antitussive effect of Ver-CA. A further acute toxicity study showed that the LD50 values of Ver-CA were 3 times that of verticinone. Conclusion: Based on the studies of pharmacology and acute toxicity, the salt has a synergic and attenuated toxicity compared with single verticinone and cholic acid. Moreover, the present study also suggests that Ver-CA, a potential novel antitussive agent, may exert its antitussive effect via both the peripheral (modulated by ATP-sensitive K+ channels) and central mechanisms (modulated by the opioid receptor).