Bioassays of total alkaloids of S. tuberosa samples representing the four types of chemical profiles were conducted on guinea pigs using citric acid aerosol for inducing cough. These results demonstrated their antitussive properties and thus suggested the possibility of other antitussive alkaloids than neotuberostemonine in S. tuberosa. So it became necessary to identify the major components in the samples of S. tuberosa representing the four types of chemical profiles. / Bioassays on guinea pigs of the four major components of S. tuberosa demonstrated their antitussive properties. Except a lower potency in tuberostemonine, antitussive effects of croomine and stemoninine showed similar or even stronger potency than neotuberostemonine at 25 and 50 mg/kg by intragastric administration. These four antitussive alkaloids could be used as lead compounds for the development of new antitussive drugs and as bioactive markers in quality control of the herb S. tuberosa and related products. / Cough is an airway defensive reflex, which is responsible for keeping the airway free of obstruction and harmful substances. As the commonest symptom for which medical advices is sought, enormous costs are spent on cough treatments. Regretfully, currently used antitussives are less than satisfactory due to their low potency or obvious side effects. So it is necessary to continue developing new and better antitussives. / Electrical stimulation of the superior laryngeal nerve on guinea pigs at 100 mg/kg through intraperitoneal administration indicated that croomine acted on the central pathway of cough reflex accompanied by respiratory depression. On the other hand, neotuberostemonine, tuberostemonine and stemoninine acted on the peripheral pathway without any observable side effects. These three alkaloids could be promising for developing new peripherally acting antitussives. Further, tuberostemonine was tested on primary cultured nodose ganglion cells by patch clamp and, at 0.5 mM, was demonstrated to significantly decrease the change amplitude of membrane potential induced by 1.0 mM citric acid solution. The results suggested that tuberostemonine could depress electrical excitability of nodose ganglion cells and thus inhibit the afferent signals of cough reflex leading to its antitussive activity. / In order to determine if the different chemical profiles of Stemona total alkaloids were the result of species difference or variations within the same species, the three Stemona species registered in the PRC Pharmacopoeia were collected from different areas in China. They were planted to flowering in our greenhouse and authenticated by both reproductive and vegetative characters. Microscopic examination on these authentic species showed that tuberous roots of S. tuberosa differed by epidermal cells with smooth outer surface and fibers in the cortex and pith from those of S. japonica and S. sessilifolia. The chemical profiles of authentic samples were analyzed on a HPLC-ELSD system. The results indicated that species-specific differences were present in the HPLC profiles of the three Stemona species. Within S. tuberosa, the chemical profiles of different samples were found to be very variable and they could be roughly divided into four types in the tested samples. Neotuberostemonine was present in one of the four types of S. tuberosa. Since antitussive effects of neotuberostemonine were demonstrated by Chung et al. (2003), it became necessary to determine if the samples containing alkaloids other than neotuberostemonine had antitussive properties. / The Chinese herb Radix Stemonae (Baibu) has long been used as an antitussive in Chinese medicine for some two thousand years. Its source materials, according to the Pharmacopoeia of the People's Republic of China (PRC Pharmacopoeia), come from the tuberous roots of three Stemona species, namely, S. japonica (Blume) Miq., S. sessilifolia (Miq.) Miq. and S. tuberosa Lour. However, hardly any experimental study is available to document their antitussive functions. Chung et al. (2003) reported that the antitussive components of S. tuberosa were neotuberostemonine and related stenine type Stemona alkaloids. And the antitussive potency of neotuberostemonine through intraperitoneal administration was reported to be comparable to codeine but not involving opioid receptors. In continuation with the study of the antitussive properties of the herb, it was found that total alkaloids of different samples of the herb appeared to vary in chemical profiles, whereas neotuberostemonine was found in only a few samples. / The major components of S. tuberosa including stemoninine, croomine and neotuberostemonine were isolated and determined by spectroscopic methods. It was the first time to isolate croomine from Stemona species, lending support to retaining the two genera Stemona and Croomina in the family Stemonaceae according to chemotaxonomy. Tuberostemonine, another major component of S. tuberosa was also isolated and determined in our team. Neotuberostemonine and tuberostemonine were two isomers but mutually exclusive in our tested samples. Moreover, these major components of S. tuberosa belonged to three types in molecular structure. Stemoninine was stemonamide type, croomine tuberostemospironine type and both neotuberostemonine and tuberostemonine stenine type. These results suggested that antitussive effects of S. tuberosa might be related to the components belonging to these three molecular types. / Xu Yantong. / "March 2006." / Adviser: Paul But. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6231. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 137-155). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_343722 |
| Date | January 2006 |
| Contributors | Xu, Yantong., Chinese University of Hong Kong Graduate School. Division of Biology. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, theses |
| Format | electronic resource, microform, microfiche, 1 online resource (xix, 169 p. : ill.) |
| Coverage | China |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
Page generated in 0.003 seconds