Mechanisms responsible for the bronchodilator activities of Tinospora crispa extracts and purified metabolites on isolated guinea-pig trachea

S Praman1, MJ Mulvany2, DE Williams3, RJ Andersen3, C Jansakul1. 1Prince of Songkla University, Department of Physiology, Faculty of Science, 90112, Thailand, 2Aarhus University, Department of Pharmacology, Denmark, 3University of British Columbia, Department of Chemistry and Department of Earth & Ocean Sciences, V6T 1Z3, Canada

Extracts from Tinospora crispa have been used in Thai folk medicine for many purposes including the treatment of asthma. Our aim was to investigate these effects and to identify the active constituents responsible for their bronchodilator activities. Ground dried stems of T. crispa were extracted with hot water and partition extracted with n-butanol. The n-butanol extract was then fractionated by column chromatography and semi-preparative C18 reversed phase HPLC. The isolated compounds were characterized by mass spectroscopy and 1H and 13C NMR spectroscopy. Studies were performed in vitro using isolated guinea pig tracheal rings. Drugs were dissolved in distilled water or 10% DMSO. Cumulative concentration-response curves were isometrically recorded by a Grass Polygraph (Grass Instrument, USA). Data are expressed as a mean ± S.E.M. (n = 4–6 animals). Tests of significance were made using the Student’s paired t-test. In all cases, a p value of 0.05 or less was considered statistically significant.The n-butanol soluble T. crispa extract caused a relaxation of the isolated trachea precontracted with carbamylcholine chloride. Propronolol or ICI-118,551 (selective β2-adrenoceptor antagonist) caused a parallel shift of the concentration-response (C-R) curve. Neither atenolol, DMPX nor suramin modified the tracheal dilatation of the T. crispa extract. Twelve compounds: adenine, adenosine, uridine, higenamine, salsolinol, tyramine, litcubinine, syringin and borapetoside A, B, D and E, were isolated from the T. crispa extract. However only 5 of them: higenamine, salsolinol, tyramine, adenosine and uridine caused a relaxation of the isolated tracheal rings. The tracheal dilatory activity of the higenamine, salsolino and tyramine were significantly inhibited by ICI-118,551. The trachial dilatory C-R curves produced by adenosine and uridine were not modified by DMPX or suramin. These results indicated that the tracheal dilatory effect of the T. crispa extract resulted from the synergistic action of at least 5 compounds: higenamine, salsolinol, tyramine via the β2-adrenergic receptors, and adenosine and uridine via other pathways.