From the vasodilator and hypotensive effects of an extract fraction from Agelanthus dodoneifolius (DC) Danser (Loranthaceae) to the active compound dodoneine

Effects of the different fractions obtained by partition of ethanolic extract (EE) of Agelanthus dodoneifolius through column chromatography were investigated on rat blood pressure and aortic relaxation and compared to those observed in the presence of crude EE. The acute hypotensive activity of EE, fractions and dodoneine, administrated intravenously, was evaluated in anaesthetized rats using the invasive method of blood pressure recording. Bioassay-guided fractionation using rat aorta pre-contracted by norepinephrine to monitor the relaxant activity led to the isolation of dodoneine. In normotensive rats, injection of EE (0.01–10mg/kg) produced a dose-dependent decrease in both systolic and diastolic blood pressure without any significant change in heart rate. In a similar way, the EE (0.001–3mg/mL) caused relaxation of rat pre-contracted aorta in a concentration-dependent manner. Fractionation of the EE afforded 14 fractions, F1–F14, that were tested on rat precontracted aortic rings. At the concentration level of 1mg/mL, a maximum relaxation effect was observed for fractions F2–F5. F4 was the most effective to elicit a concentration-dependent relaxation effect with an ED50=160±1.1 μg/mL (n=5) and to decreased systolic and diastolic control pressure by 56.9% and 81.6% respectively. F4 contains most of the dihydropyranone dodoneine, with 93% of the sample mass. Dodoneine separated from this fraction was also able to decrease both systolic and diastolic arterial pressure by 32.5% and 38.7% at 100μg/kg, respectively. For the first time, this study demonstrates the hypotensive property of the dodoneine present in Agelanthus dodoneifolius.