Hypotensive and vasorelaxant effects of the procyanidin fraction from Guazuma ulmifolia bark in normotensive and hypertensive rats

The aim of the study: was to investigate the in vivo and in vitro cardiovascular activity of a procyanidin fraction (PCF) obtained from acetone extract of Guazuma ulmifolia bark which has traditionally been used as an antihypertensive agent. Results: 10 mg/kg PCF doses orally administered to sugar-fed hypertensive rats decreased both the systolic arterial pressure and the heart rate, whereas the same doses intravenously administered induced arterial hypotension which was attenuated by N-G-nitro-L-arginine methylester (L-NAME 31 mg/kg) pretreatment. In these experiments we employed carbachol as a positive control test. The PCF reduced the contraction induced by norepinephrine (1 x 10(-7) M) in isolated aortic rings of normotensive (IC50 = 35.3 +/- 12.4 ng/mL) and sugar-fed hypertensive (IC50 = 101.3 +/- 57.2 ng/mL) rats. This relaxant activity was inhibited by either vascular endothelium removal or L-NAME (30 mu M) pretreatment, while indomethacin (10 mu M) or atropine (10 mu M) had no effect. Preliminary analysis of the PCF by HPLC-DAD-MS and FAB(+) mass spectrometry allowed the detection of the main components such as the complex of procyanidin oligomers consisting mainly of tetramers and trimers. Conclusions: Guazuma ulmifolia bark possesses long-lasting antihypertensive and vasorelaxing properties linked to the endothelium related factors, where nitric oxide is involved. (C) 2008 Elsevier Ireland Ltd. All rights reserved.