Purpose. A series of derivatives having a propranolol-like moiety linked to NO-donor furoxan substructures were synthesized. The main objective of this investigation was to obtain agents with mixed No-dependent vasodilating and beta-blocking activities.Methods. Most of the target compounds were synthesized from the appropriate furoxans bearing XCH2CH2NH2 (X = O, S, SO2) chains at the 4 position of the ring, using AI(C2H5)(3) in methylene chloride solution and (+/-)2,3-epoxypropyl 1-naphtyl ether. Two of the final products (X = CONH) were obtained by coupling the appropriate furoxancarboxylic acids with N-[2-hydroxy-3-(1-naphthoxy)propyl]ethylenediamine. beta(1)- and beta(2)-blocking activities were examined on isolated guinea pig right atria and on guinea pig trachea respectively. Vasodilating properties were assessed on endothelium denuded strips of rat aortaResult. Some derivatives behave as well balanced "hybrids" displaying NO-dependent vasodilating and beta-blocking properties in the same concentration range. Some others display either prevalent beta-blocking or vasodilating activity. Generally speaking hybrid formation lowers the affinity for beta-receptors, in particular for beta(2)-type, to give an increase in beta(1)/beta(2) selectivity.Conclusions. The furoxan system is a flexible tool in designing analogues of propranolol whose NO-donating and beta-blocking properties are modulated over a wide range.
The synthesis, characterization, NO donor properties, and in vitro vasodilating activity of a series of water soluble furoxans (5-14a,b) are described. AU of the compounds released NO when treated with a large excess of cysteine under physiological conditions (pH 7.4; 37 degrees C). The amount of NO produced after 1 h of incubation was evaluated by detecting nitrites, via the Griess reaction. Derivatives 5b, 7b, and 14b were able to release nitric oxide also in the absence of the thiol cofactor. The initial rates of NO release were determined at different concentrations, using a spectrophotometric technique based on the NO-induced oxidation of oxyhemoglobin (HbO(2)) to methemoglobin (MetHb). The initial rates of NO release were Linearly dependent on the concentrations of the single compounds. The vasodilating potency (EC(50)) of all the derivatives was assessed on rat aortic. strips precontracted with noradrenaline. Correlation between potency and initial NO release rate is discussed.