Abstract

Terminalia arjuna, Roxb barks has a folkloric repute to possess spasmolytic, bronchodilator and
cardiotonic, properties. The present study was undertaken to evaluate possible effects of
methanolic extract of barks of Terminalia arjuna (Ta.Cr) in gastrointestinal, respiratory and
cardiovascular systems via in vitro experiments to rationalize its use in traditional system of
medicine. The phytochemical analysis of crude methanolic extract of Terminalia arjuna barks
revealed the presence of tannins and saponins as methanol soluble extractable constituents. The
spontaneous contractions in isolated rabbit jejunum were relaxed at tissue bath concentrations of
0.01-5.0 mg/ml, however, addition of propranolol to the tissue bath reduced the extent of
relaxation and same level of effect was achieved at increased concentrations, i.e., 0.1-10.0
mg/ml. The Ta.Cr showed a weak relaxant effect on high K+

(80 mM) low K+

(25 mM) and
carbachol (1 μM)-induced contractions. Similarly, it also caused partial relaxation of high K+ (80
mM) and low K+ (25 mM)-induced contractions in isolated rabbit tracheal preparations.
However, it relaxed completely the carbachol (1 μM)-induced contractions, but addition of
propranolol (1 μM) to the tissue bath minimized the relaxant effect. Moreover, the Ta.Cr caused
partial relaxation of the phenylephrine (1 μM)-induced contractions in isolated rabbit aorta
preparations. Furthermore, the Ta.Cr showed a positive inotropic and positive chronotropic
effects at lower tissue bath concentrations in isolated rabbit paired atria preparations but these
effects were found to be antagonized by the presence of propranolol in the tissue bath. Further
addition of Ta.Cr to the tissue bath caused a decrease in the magnitude of observed inotropic and
chronotropic effects in isolated rabbit paired atria; which was found to be abolished on addition
of atropine. Thus; in conclusion, the crude methanolic extract of barks of Terminalia arjuna,
Roxb exhibited spasmolytic, bronchodilator and cardiotonic properties which are likely to be
mediated through presence of dominant β-adrenergic agonistic activity along with presence of
some weak muscarininc agonistic activity.