The relaxant activity of the methanolic extract of Acanthus montanus on intestinal smooth muscles

The effects of the methanolic extract of Acanthus montanus on different smooth muscle preparations have been investigated. The extract (6.25-100 mu g/ml) produced a concentration-dependent relaxation and inhibition of the spontaneous contraction of the rabbit jejunum which was reversed by CaCl2 (0.1-1mM). This effect of the extract was not blocked by propranolol (3 x 10(-7) M) but partially antagonised by phentolamine (10(-6)-3 x 10(-6) M), procaine (10(-3) M) and methylene blue (10(-5) M). The extract also caused a concentration-dependent relaxation of the KCl-precontracted taenia coli of the guinea-pig which was partially blocked by propranolol (3 x 10(-5) M) that completely blocked isoprenaline (10(-8)-3 x 10(-4) M) relaxation of the tissue. Methylene blue (10(-5) M) and procaine (10(-3) M) completely blocked the direct relaxant effects of the extract and isoprenaline on the guinea-pig taenia coli. The extract (0.1-1 mg/ml) shifted the concentration-response curves of CaCl2 to the right in a concentration-dependent manner on the guinea-pig taenia coli. These effects of the extract suggest a non specific smooth muscle relaxant activity. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.