HYPOTENSIVE EFFECT OF O-METHYLISOTHALICBERINE, A BISBENZYLISOQUINOLINE ALKALOID ISOLATED FROM BERBERIS-CHILENSIS ON NORMOTENSIVE RATS

O-Methylisothalicberine (O-MI) is a bisbenzylisoquinoline alkaloid iso lated from Berberis chilensis, structurally similar to alkaloids previ ously described in the literature as calcium antagonists of natural or igin (berbamine, tetrandrine, antioquine, 7-O-demethylisothalicberine and others). O-MI caused a significant reduction of mean arterial pres sure (MAP) in normotensive anaesthetized rats. Doses of 1.0; 2.5; 5.0; 7.5 and 10.0 mg/kg were administered via the femoral vein. MAP was re duced by 5.8%; 10.1%; 35.6%; 67.9% and 60.5% respectively. The onset o f hypotensive action was 5 s after 5 mg/kg i.v. and the effect lasted for about 120 s. O-MI exhibited an LD50 of 5 mg/mL towards the brine s hrimp (Artemia salina). (C) 1997 by John Wiley & Sons, Ltd.