Vasoactive effects of different fractions from two Panamanians plants used in Amerindian traditional medicine

Ethnopharmacological relevance: Cecropia obtusifolia (Cecropiaceae) and Psychotria poeppigiana (Synonym: Cephaelis elata, Rubiaceae) are two Latin American plants broadly used in traditional Amerindian medicine. The former, together with many other species of the genus Cecropia, share the folk reputation of curing heart failure, cough, asthma and bronchitis. The latter is used in Panama by Kuna and Ngäbe Buglé (Guaymies) native Indians for the treatment of dyspnea. Aim of the study: Based on screening of selected medicinal Panamanian plants by radioligand-binding techniques by , the present study was carried out in order to investigate the vasoactive effects of different fractions from both P. poeppigiana and C. obtusifolia on rat thoracic aorta and identify active fractions and their chemical constituents. Materials and methods: Both acid and neutral methanol fractions (P-AMeOH and P-NMeOH) and acid and neutral dichlorometane fractions (P-ADCM and P-NDCM) were obtained from P. poeppigiana crude methanolic and dichlorometane extracts, respectively. Identical fractionation was carried out for C. obtusifolia (C-AMeOH, C-NMeOH, C-ADCM and C-NDCM. Vasorelaxant effect of all fractions, and their inhibition of contractile responses to angiotensin II were evaluated in isolated aortic rings. Results: P-AMeOH, P-NMeOH and P-ADCM fractions induced a concentration-dependent relaxation (43.9±1.8%, 35.3±4.7% and 52.9±3.5%, respectively) in the endothelium-intact aorta precontracted by phenylephrine (PE, 10⁻⁶ M). The relaxation produced by C-AMeOH and C-NMeOH (57.3±2.5% and 53.3±3.3%, respectively) was greater than the effect produced by C-ADCM and C-NDCM (42.2±3.4% and 21.8±0.8%, respectively). Only the incubation of the aortic rings with P-AMeOH reduced the maximum contraction induced by angiotensin II at 20.08±0.55%. Conclusions: The direct vasorelaxation effect observed could explain in part the ethnomedical use of these plants in Amerindian traditional medicine. The most active fractions contain phenolic and aromatic acid compounds. Furthermore, P-AMeOH, the only fraction that showed both vasorelaxant effect and inhibition of contractile responses to angiotensin II, is the most rich in aromatic acids compounds and the only one that contains scopoletin.