HERBAL MEDICINE CATUAMA INDUCES ENDOTHELIUM-DEPENDENT AND ENDOTHELIUM-INDEPENDENT VASORELAXANT ACTION ON ISOLATED VESSELS FROM RATS, GUINEA-PIGS AND RABBITS

The present study was designed to examine the vasorelaxant action of t he herbal medicine Catuama and the hydroalcoholic extracts (HE) of eac h plant present in this product and to compare their effects with that caused by acetylcholine (ACh) in intact ((+)E) or in endothelium-rubb ed ((-)E) rings of rat thoracic aorta (RA), guinea-pig pulmonary arter y (GPPA), guinea-pig mesenteric artery (GPMA), rabbit pulmonary artery (RPA) and rabbit mesenteric artery (RMA) precontracted with noradrena line (NA) or phenylephrine (PE). The extract of Catuama (1-3000 mu g/m L) produced graded relaxation of RA, (+)E or (-)E, with mean EC(50) of 430 mu g/mL and congruent to 3000 mu g/mL and E(max) of 81%+/-15% and 47%+/-4%, respectively. The nitric oxide (NO) synthase inhibitor, N-o mega-nitro-L-arginine (L-NOARG, 100 mu M), inhibited its vasorelaxant action (p<0.05) in RA ((+)E), while indomethacin (3 mu M), propranolol (1 mu M), glibenclamide (1 mu M), methylene blue (10 mu M) and apamin (0.1 mu M) had no significant effect. ACh (1-1000 mu M) caused graded relaxation in RA with (+)E, these effects being markedly antagonized by L-NOARG (100 mu M), by methylene blue (10 mu M) and partially by ap amin (0.1 mu M), but not by indomethacin (3 mu M), glibenclamide (1 mu M) or propranolol (1 mu M). The Catuama extract (1-3000 mu g/mL) prod uces partial relaxations in rings of RMA (mean EC(50) of 1073 mu g/mL and E(max) 56%+/-13%), an effect which was antagonized by L-NOARG (100 mu M). In RPA ((+)E) the extract produces partial relaxation followed by contraction (E(max) 28%+/-6% ), an effect which was abolished by L -NOARG (100 mu M) or methylene blue (10 mu M). The extract caused grad ed relaxation in rings of GPPA and GPMA with mean EC(50) values of 60 mu g/mL and 1148 mu g/mL and E(max) 96%+/-2% and 88%+/-12%, respective ly, L-NOARG (100 mu M) blocked the Catuama extract vasorelaxation In G PPA and only partially in GPMA, but markedly antagonized the vasorelax ations caused by ACh in both GPPA and RMA. The HE Paullinea cupana, Zi nziber officinalis and Trichilia catigua (1-3000 mu g/mL) caused a gra ded vasorelaxant effect (+)E of RA with a mean EC(50) of 22, 55 and 17 93 mu g/mL and E(max) 100%, 86%+/-7%, 70%+/-2%, respectively. In addit ion, the HE of P. cupana also caused graded relaxation in (-)E of RA w ith EC(50) and E(max) of 233 mu g/mL and 100%, respectively, while T. catigua and Z. officinalis produced partial relaxation in RA (+)E. In contrast the HE of Ptychopetalum olacoides caused little contraction ( 46%+/-14%). These results demonstrate that the medicinal herb Catuama produces significant vasorelaxation responses in vessels from differen t animal species, and show that its effects are in great part dependen t on the release of NO or NO-derived substances. Our results also demo nstrate that the vasorelaxant action of the product Catuama seems to b e due to the action of the active principles present mainly in P. capu na; T. catigua and, to a lesser extent, in Z. officinalis. Such result s may contribute to the explanation of its beneficial effect of Catuam a herbal medicine in the management of cardiovascular disturbances. (C ) 1997 by John Wiley & Sons, Ltd.