Guazuma ulmifolia Lam. bark is used in Panama traditional medicine for the treatment of arterial hypertension [1]. The phytochemical studies carried on with G. ulmifolia bark, have led to the isolation of procyanidins. These compounds have also been related to antihypertensive activities. The hypotensive and vasorelaxant effect of a procyanidin complex (PACC) prepared from G. ulmifolia bark was investigated in normotensive and hypertensive rats, and in rat aortic rings. The oral administration of PACC (10mg/kg) to conscious normotensive or hypertensive rats decreases the systolic arterial pressure (SAP) and the heart rate (HR). The intravenous administration of same fraction (10mg/kg) in anesthetized rats induced arterial hypotension that was attenuated by pre-treatment with NG-nitro-L-arginine-methylester (L-NAME 31mg/kg). In isolated aortic rings of normotensive and hypertensive rats, the PACC reduced the contraction induced by norepinephrine (1X10-7 M). The IC50 doses was 35.3±12 ng/mL and 101±57 ng/mL in isolated aortas of normotensive and hypertensive rats, respectively. This relaxant activity was inhibited by either removal of vascular endothelium or pre-treatment with L-NAME (30µM), while indomethacin (10µM) or atropine (10µM) had no effect. Preliminary analysis of the PACC by HPLC-PAD-/MS and FAB+ mass spectrometry allowed detection of the main components as a complex of procyanidin oligomers consisting mainly of type B procyanidins. These findings suggest that cardiovascular effects from G. ulmifolia are due to the procyanidin complex, while the antihypertensive mechanism was found to be linked to endothelium related factors, where nitric oxide is know to be involved.
Acknowledgements: Consejo Nacional de Ciencias y Tecnología, CONACYT, México for financial support through projects MO292 and Q42096.
Reference: 1. Caballero-George, C. et al. (2001), Phytomedicine 8: 59–70.
