Preliminary mechanistic studies on the smooth muscle relaxant effect of hydroalcoholic extract of Curcuma caesia.

Abstract

Background and objectives: Curcuma caesia (family Zingiberaceae) is widely used in India as both an anti-inflammatory and anti-asthmatic in Ayurvedic medicine. However, there are no published pharmacological data on Curcuma caesia on its potential anti-asthmatic activity. Hence, the objective of the present investigation is to study the mechanisms by which the hydroalcoholic extract of Curcuma caesia relaxes the smooth muscle in the bronchioles and vasculature of the respiratory tract.

Methods: The hydroalcoholic extract of Curcuma caesia (CC extract) was tested for its per se relaxant effect in guinea pig trachea and also in the presence of various receptor antagonists and enzyme inhibitors namely propranalol, 2', 5'-dideoxyadenosine, methylene blue, glibenclamide, N(omega)-nitro-L-arginine (L-NNA) and alpha-chymotrypsin. Furthermore, the possible role of hydroalcoholic extract in calcium channel modulation was investigated in depolarized rabbit aorta.

Results: The CC extract concentration dependently relaxed the carbachol (1 microM)-induced pre-contractions; the IC50 value was found to be 239.36 microg/ml and the incubation of either receptor antagonists or enzyme inhibitors did not exhibit any effect on the relaxation. In the isotonic Ca2+-free high-K+ (60 mM) depolarized aorta, CC extract (30 microg/ml) inhibited concentration-response curves of cumulative Ca2+ (0.1-30 mM) and the PD'2 value was found to be 4.11 microg/ml.

Interpretation and conclusion: The extract showed a dose-dependent, non-specific relaxation of pre-contracted isolated guinea pig trachea. The non-specific relaxant effect of the extract may be due to its ability to modulate calcium activity.