Effect of a new pyrimidine derivative, 2-(4´-aminobenzenamine)-pyrimidine, isolated from the bulbs of Autonoë madeirensis, in the rat vas deferens contractility.

Abstract

Autonoë madeirensis (Menezes) Speta is a Hyacinthaceae endemic from the Madeira Archipelago (Portugal). From its bulbs we isolated a new compound: 2-(4-aminobenzenamine)-pyrimidine [1]. As pyrimidines have important effects in smooth muscle contraction we investigated the effect of the ethanolic extract and the effect of compound [1] in the rat vas deferens contractility. Compound [1] was obtained from fresh bulbs extracted with ethanol. The ethanolic residue was subjected to fractionation yielding the pure compound [1] identified by spectral data. Using isolated rat vas deferens, dose-response curves were obtained with phenylephrine (Phe) (1.0–32.0 µM) in the absence and in the presence of the ethanolic extract and in the presence of compound [1]. Both ethanolic extract and compound [1] in concentrations devoid of effect shifted to the right the concentration-response curve of Phe, without changing the maximal effect. EC50 values for Phe increased in the presence of compound [1] (5 µM, 50 µM and 100 µM) and were respectively 3 ± 0.8 µM, 4.6 ± 0.7 µM and 3.9 ± 0.6 µM. These values are statistically different from EC50 values obtained in the same vas in control conditions which were respectively 2.2 ±0.8 µM, 1.7 ± 0.2 µM and 1.5 ± 0.1 µM. In the presence of the extract (0.3 and 1.2 mg/ml) the EC50 values for Phe increased significantly and were respectively 4.1 ± 0.8 µM versus 2.2 ± 0.3 µM in control and 4.6 ± 0.9 µM versus 1.7 ± 0.2 µM in control. These results suggest that compound [1] antagonises the α-adrenergic effects of Phe in the rat vas deferens.