Antitussive and central respiratory depressant effects of Stemona tuberosa.
OBJECTIVE
Stemona alkaloids with distinctly different chemical skeletons are recently reported as the active components in the antitussive herb Baibu derived from the root-tubers of Stemona tuberosa. This study aims to determine if alkaloids of this herb contribute equally to the antitussive functions, act on the same sites of cough reflex, and play any role in inducing central respiratory depressant effects.


METHODS
Antitussive potency of four major alkaloids was evaluated on guinea pigs with citric acid aerosol to induce cough. The action sites of the alkaloids on cough reflex pathway were tested with electrical stimulation of the superior laryngeal nerve in guinea pigs. The central respiratory effects of croomine were also tested on guinea pigs.


RESULTS
Croomine, neotuberostemonine and stemoninine showed similar antitussive potency, while tuberostemonine showed much weaker antitussive potency. Neotuberostemonine, tuberostemonine and stemoninine acted on the peripheral cough reflex pathway, while croomine acted on the central part. Croomine also showed obvious central respiratory depressant effects.


CONCLUSIONS
The four major Stemona alkaloids in Stemona tuberosa do not contribute equally to antitussive potency in guinea pigs. Neotuberostemonine, tuberostemonine and stemoninine target on peripheral cough reflex pathway. Croomine acts on central sites in the cough reflex pathway and demonstrates central respiratory depressant effects, which can partly account for the adverse reactions reported for the herb.
Xu
Yan-Tong
YT
Department of Biology, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, PR China.
Shaw
Pang-Chui
PC
Jiang
Ren-Wang
RW
Hon
Po-Ming
PM
Chan
Yiu-Man
YM
But
Paul Pui-Hay
PP
D000470:Alkaloids / Q000494:pharmacology / Q000627:therapeutic use; D000818:Animals; D000996:Antitussive Agents / Q000494:pharmacology* / Q000627:therapeutic use; D002491:Central Nervous System Agents / Q000494:pharmacology / Q000627:therapeutic use; D019343:Citric Acid / Q000494:pharmacology; D003371:Cough / Q000188:drug therapy*; D006168:Guinea Pigs; D007783:Lactones; D007823:Laryngeal Nerves / Q000187:drug effects; D018517:Plant Roots / Q000737:chemistry; D011759:Pyrrolidines; D012137:Respiratory System / Q000187:drug effects; D013141:Spiro Compounds; D041901:Stemonaceae / Q000737:chemistry*
D000470:Alkaloids; D000996:Antitussive Agents; D002491:Central Nervous System Agents; D007783:Lactones; D011759:Pyrrolidines; D013141:Spiro Compounds; C468415:neotuberostemonine; D019343:Citric Acid; C034243:tuberostemonine; C082845:croomine