OBJECTIVETo examine the relaxant effects of hydro-ethanolic, macerated aqueous (MA) and lipidfree macerated aqueous (LFMA) extract of Tymus vulgaris on tracheal chains of guinea pigs.

METHODSThe relaxant effects of five cumulative concentrations of each extract (0.4, 0.8, 1.2, 1.6 and 2.0 g/100 mL) were compared with saline as negative control and five cumulative concentrations of theophylline (0.1, 0.2, 0.4, 0.6 and 0.8 mmol/L) on precontracted tracheal smooth muscle of guinea pig with 60 mmol/L KCl (group 1) and 10 µmol/L methacholine (group 2, n=6 for each group).

RESULTSIn group 1 all concentrations of theophylline, three higher concentrations of hydro-ethanolic, two concentrations of LFMA and last concentration of MA extracts showed significant relaxant effects compared with that of saline (P<0.05 or P<0.01). Two lower concentrations of LFMA and all concentrations of MA except higher one caused contraction compared with saline (P<0.05 or 0.01). In group 2 experiments, all concentrations of theophylline, hydro-ethanolic, MA and LFMA extracts showed significant relaxant effects compared to that of saline (P<0.05 or P<0.01). In both groups, the relaxant effect of all concentrations of hydro-ethanolic extract were significantly higher than most concentrations of others (P<0.05 or P<0.01). The relaxant effect of different concentrations of three extracts were significantly greater in group 2 compared with group 1 experiments (all P<0.01). There were significantly positive correlations between the relaxant effects and concentrations for theophylline and all extracts in both groups (P<0.05 or P<0.01).

CONCLUSIONHydro-ethanolic extract has a potent weaker relaxant effect for other extracts from Tymus vulgaris on tracheal chains of guinea pigs.