Herbal medicine Catuama induces endothelium‐dependent and ‐independent vasorelaxant action on isolated vessels from rats, guinea‐pigs and rabbits

The present study was designed to examine the vasorelaxant action of the herbal medicine Catuama and the hydroalcoholic extracts (HE) of each plant present in this product and to compare their effects with that caused by acetylcholine (ACh) in intact (+E) or in endothelium‐rubbed (−E) rings of rat thoracic aorta (RA), guinea‐pig pulmonary artery (GPPA), guinea‐pig mesenteric artery (GPMA), rabbit pulmonary artery (RPA), rabbit mesenteric artery (RMA) precontracted with noradrenaline (NA) or phenylephrine (PE). The extract of Catuama (1‐3000 μg/mL) produced graded relaxation of RA, +E or −E, with mean EC50 of 430 μg/mL and ≊ 3000 μg/mL and Emax of 81 % ± 15 % and 47% ± 4 %, respectively. The nitric oxide (NO) synthase inhibitor, Nω‐nitro‐L‐arginine (L‐NOARG, 100 μM), inhibited in vasorelaxant action (p < 0.05) in RA (+E), while indomethacin (3 μM), propranolol (1 μM), glibenclamide (1 μM), methylene blue (10 μM) and apamin (0.1 μM) had no significant effect. ACh (1‐1000 μM) caused graded relaxation in RA with +E, these effects being markedly antagonized by L‐NOARG (100 μM), methylene blue (10 μM) and partially by apamin (0.1 μM), but not by indomethacin (3 μM), glibenclamide (1 μM) or propranolol (1 μM). The Catuama extract (1‐3000 μg/mL) produces partial relaxations in rings of RMA (mean EC50 of 1073 μg7/ml and Emax of 56 % ± 13 %), an effect which was antagonized by L‐NOARG (100 μM). In RPA (+E) the extract produces partial relaxation followed by contraction (Emax 28 % ± 6 %), an effect which was abolished by L‐NOARG (100 μM) or methylene blue (10 μM). The extract caused graded relaxation in rings of GPPA and GPMA with mean EC50 values of 60 μg/mL and 1148 μg/mL and Emax 96% ± 2% and 88% ± 12%, respectively. L‐NOARG (100 μM) blocked the Catuama extract vasorelaxation in GPPA and only partially in GPMA, but markedly antagonized the vasorelaxations caused by ACh in both GPPA andRMA. The HE Paullinea cupana, Zinziber officinalis and Trichilia catigua (1‐3000 μg/mL) caused a graded vasorelaxant effect +E of RA with a mean EC50 of 22, 55 and 1793 μg/mL and Emax 100%, 86% ± 7% 70% ± 2%, respectively. In addition the HE of P. cupana also caused graded relaxation in −E of RA with EC50 and Emax of 233 μg/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 different animal species, and show that its effects are in great part dependent on the release of NO or NO‐derived substances. Our results also demonstrate that the vasorelaxant action of the product Catuama seems to be due to the action of the active principles present mainly in P. cupana; T. catigua and, to a lesser extent, in Z. officinalis. Such results may contribute to the explanation of its beneficial effect of Catuama herbal medicine in the management of cardiovascular disturbances. © 1997 John Wiley & Sons, Ltd.