[Inhibition of platelet aggregation by 1,2,3,4-tetrahydro-beta-carbolines: evidence for 5-hydroxytryptamine antagonistic activities (author's transl)]

New NO-donors with antithrombotic and vasodilating activities, Part 14. 1,3,4-Triazol-1-oles

Five 1,3,4-triazol-1-oles (5a-f) with different alkyl, aryl, and arylalkyl substituents in 2,5-position were synthesized and tested for their antithrombotic properties. The 2,5-dimethyl derivative 5a was most active. 2 h after administration of 60 mg/kg to rats thrombus formation by a laser beam was inhibited by 42% in arterioles and by 33% in venules. At the same dose the blood pressure of SHR rats was slightly (5%) but significantly decreased even 4 h after application of 5a. This pattern of activities suggests a nitric oxide mediated mechanism of action. 1,1'-Azo-bis-ethanone oxime(7)-the synthetic precursor of 5a-inhibited the aggregation of blood platelet (Born test) with an IC50 = 15 mumol/L.

New NO-donors with antithrombotic and vasodilating activities, part 15 nitrolic acids

Five 1-oximino-1-nitro compounds (nitrolic acids) were prepared and tested for antithrombotic and blood pressure lowering activities. 1-Nitro-ethanone 1-oxime (1, ethylnitrolic acid) 2 h after oral administration to rats inhibited thrombus formation by a laser beam in mesenteric arterioles of rats by 69% and by 46% in venules (60 mg/kg). The blood pressure of SHR rats even at this high dose only was decreased by 10% suggesting that antithrombotic and blood pressure effects can be dissociated. The in vitro decomposition of 1 at 37 degrees C nearly exclusively gave N2O and acetic acid indicating that HNO primarily had been formed.

Platelet aggregation inhibiting and anticoagulant effects of oligoamines, XXVI: Antiplatelet and antithrombotic effects of the oligoamine RE 1492 in combination with standard and future antithrombotic drugs

The combined effects of the oligoamine RE 1492 with the NO-donor RE 2047 or ASA, ticlopidine, pentoxifylline and BM 14515 were determined in vitro (Born-test) and in vivo (rat thrombosis model). The effects in vitro were supra additive but over independent. In vivo all combinations showed over additive and over independent inhibition of thrombus formation. The best results were obtained with a combination of 10 mg/kg RE 1492C and 10 mg/kg RE 2047. It inhibited thrombus formation in arterioles (A) by 79% and 36% in venoles (V). The combined effect of RE 1492C and pentoxifylline 10 mg/kg each was 62% (A) or 32% (V), respectively.

New NO-donors with antithrombotic and vasodilating activities, II: 3-alkyl-N-nitroso-5-sydnone imines

Fifteen 3-alkyl-, four 3-cycloalkyl-N-nitroso-5-sydnone imines and five 3-alkyl-N-nitro-5-sydnone imines were synthesized and their ability to inhibit platelet aggregation induced by collagen (Born-test) was studied in vitro. Dependent on the chemical structure, the IC50-values for the inhibition of platelet aggregation were in the range of 0.2-140 mumol/L. It is suggested that this scale reflects different binding properties of the nitrosimines with respect to the platelet membrane. Highest activities were observed for the 3-hexyl (2f) and the 3-cyclohexyl (2p) derivative. Three nitrimines (3e, 3f, 3i) also showed IC50 values below 10 mumol/L. For the nitrosimines 2a, 2f, and 2m antithrombotic activity was demonstrated in vivo. They inhibited laser induced arterial thrombosis in anesthetized rats up to 70% two h after oral administration. In conscious renal-hypertensive dogs, the decrease in systolic blood pressure and left ventricular enddiastolic pressure suggests an antianginal activity of the compound 2a similar to that of molsidomine (M). The smoother onset and the longer duration of action of the new compound as compared to M could be a significant advantage of 2a in the therapy of angina pectoris.

New NO-donors with antithrombotic and vasodilating activities, I: 3-Arylalkyl-N-nitroso-5-sydnone imines

Nine nitrosimino title compounds were prepared. They inhibit the aggregation of human platelets induced by collagen with an IC50 = 0.7--33 mumol/L. The most active substance is the 3-phenylethyl derivative 6b. The in vitro effect is mediated by an active metabolite which is formed by a photochemical reaction in the aggregometer. As the corresponding and so far unknown sydnone-5-cyanimines have no effect on platelets the metabolite is most certainly a NO-species. The activity of the sydnone-5-nitrimine 5b is in the same order of magnitude (IC50 = 7.5 mumol/L) as in the nitrosimines of type 6. The most active compound 6b was investigated for antithrombotic properties in a thrombosis model, where the thrombus formation was induced by a laser-beam. 2 h after oral administration of 60 mg/kg of 6b to rats in venoles a 28% inhibition of thrombin formation was found. In arterioles this effect is more evident and a 48% inhibition is seen (the thrombus formation index is 2.6 and 3.9, respectively). These results suggest that the active metabolite is formed as well in vivo.

Platelet aggregation inhibiting and anticoagulant effects of oligoamines, XXII: Bisoxazol-, bisimidazol-, bisthiazol- and oligo-1,2,4-thiadiazolimines

One mesoionic 4,4'-propylene-bis-oxazol-5-imine (5), two 2,2'-m-phenylene-bis-imidazol-4-imines (9a,b), five 4,4'-benzene-bis-(and tris)-thiazol-2-amines (13a,b, 14a-c) and 14 3,3'-benzene-bis-(and tris)-1,2,4-thiadiazolimines (18a-o) were synthesized and assayed for their antiplatelet and anticoagulant activities. The most potent compound was the tris-thiadiazole derivative 18m which inhibited the aggregation of platelets induced by collagen at a concentration of 10 mumol/L by 50 percent (Born-test). No anticoagulant effects (Quick-test) were observed up to 400 mumol/L. In the thiazolamine series combined antiplatelet and anticoagulant activities were seen.

Platelet aggregation inhibiting and anticoagulant effects of oligoamines, XX: 4,4',4''-(1,3,5)-benzene-tris-sydnone imines

The synthesis of ten tris-sydnone imine derivatives, unknown up to now, is described. All compounds are alkyl or arylalkyl substituted in 3-position of the sydnone imine. The most powerful agent was the 3-propyl derivative 6c. It inhibits the aggregation of human platelets induced by collagen in a concentration of 1 mumol/L half maximally. Its N-ethoxycarbonyl derivative 7c, which was designed as a prodrug, showed only small antithrombotic effects in rats. The reason for this low degree of activity is discussed.

Platelet aggregation inhibiting and anticoagulant effects of oligoamines, XVII: Oligoamines with fluorescent properties. Part A: Fluorescent bridged nitrogen functions

Eleven dimethanamines and one disydnonimine with fluorescent properties have been synthesized. All of them show antiplatelet activities (IC50, Born-test) in concentrations between 14-75 mumol/L. Five of them inhibited fibrin formation induced by thromboplastin by more than 75% in a 200 mu molar concentration. Both effect do not run parallel. The most space consuming fluorophores show the smallest inhibition of the platelet aggregation. Best results were obtained with an azulene, acenaphthene or naphthalene moiety between the two basic nitrogen functions.