SPASMOGENIC ACTIVITY OF 1-HYDROXY-3,7,8- TRIMETHOXYXANTHONE ISOLATED FROM THE METHANOL EXTRACT OF THE STEM BARK OF ANTHOCLEISTA VOGELII PLANCH. (LOGANIACEAE) IN RATS.

Summary A novel xanthone, 1-hydroxy-3,7,8-trimethoxyxanthone (AV) isolated from the methanol extract of the stem bark of Anthocleista vogelii Planch. produced a dosedependent effect on the tone and force of the spontaneous contraction of the rat ileal and stomach smooth muscle fragments at concentrations ranging from 2.50 x 10 -2 to 1.60 µg/ml. A concentration of 8.00 x 10 -1 µg/ml of AV produced maximal contractile effect in a cumulative as well as in a single concentration. 8.00 x 10 -1 µg/ml, atropine, reduced this spasmogenic effect induced by the compound (AV) by 80.98% on ileal fragment and by 81.84% on stomach smooth muscle fragment. Similarly, the same concentration of atropine reduced the contractile effect of acetylcholine (8.00 x 10 -1 µg/ml) by 78.08% on the ileum and 100 % on the stomach fragments. Nifedipine, (1.60 x 10 -2 µg/ml) and pyrilamine maleate, (6.00 x 10 -1 µg/ml) completely inhibited the spasmogenic effect of AV in both ileal and stomach smooth muscle fragments. These results point to a possible stimulation of these muscle fragments through muscarinic receptors which increase Ca 2+ mobilisation from both extra and intramuscular medium.