Synthesis and evaluation of some xanthone derivatives for anti-arrhythmic, hypotensive properties and their affinity for adrenergic receptors.

A series of 2-, 4- or 2-methyl-6-substituted xanthone derivatives 8-17 containing selected piperazine moieties were synthesized and tested for their electrocardiographic, anti-arrhythmic, and antihypertensive activity, as well as for the alpha1- and beta1-adrenoceptor binding affinities. Of the newly synthesized derivatives, 2-(2-hydroxy-3-(4-(2-phenoxyethyl)piperazin-1-yl)propoxy)-9H-xanthen-9-one dihydrochloride 9, 4-(2-hydroxy-3-(4-(2-phenoxyethyl)piperazin-1-yl)propoxy)-9H-xanthen-9-one dihydrochloride 12, and 4-(2-(4-(pyridin-2-yl)piperazin-1-yl)ethoxy)-9H-xanthen-9-one dihydrochloride 15 possessed significant anti-arrhythmic activity in the adrenaline-induced model of arrhythmia, with the ED50 values ranging 1.7-7.2 mg/kg. Compound 15 had the lowest ED50 value equaling 1.7 mg/kg, which was comparable with ED50 value of propranolol, which was used in this test as a reference compound. Compound 9 showed also the strongest hypotensive activity, which persisted for 60 minutes at the dose of 2.5 mg/kg. 2-(2-(4-(2-Phenoxyethyl)piperazin-1-yl)ethoxy)-9H-xanthen-9-one dihydrochloride 8 also significantly lowered blood pressure at a dose of 2.5 mg/kg but much weaker than compound 9. Binding studies are in agreement with our pharmacological results and could explain anti-arrhythmic effect of compound 15 and anti-arrhythmic and hypotensive effects of compounds 9 and 12.