Synthesis, pharmacological activity and nitric oxide generation by nitrate derivatives of theophylline.

Nitrates of theophylline derivatives - potential nitric oxide (NO) donors - were synthesized by esterification of 7-hydroxyalkyl theophylline derivatives with fuming nitric acid. The nitrates obtained were tested in-vitro in reactions with sulfydryl compounds at appropriately adjusted pH and temperature. Under the applied conditions, the synthesized compounds underwent decomposition to release NO, quantified using a polarographic method using a selective isolated (ISO-NO) sensor. The effects of dyphylline and proxyphylline and their new synthesized nitrates on arterial blood pressure (BP) were measured in spontaneously hypertensive (SH) rats. BP was measured in conscious SH rats using the tail-cuff method. Both short- and long-term administration of the xanthines tested significantly decreased systolic, diastolic and mean BP. The hypotensive effect of a single dose of nitrate dyphylline on mean BP was greater than that of the parent compound (P = 0.000012; P=0.000472 at 30 and 60 min post-dose, respectively), whereas proxyphylline and its nitrate derivative had similar activity. In rats treated with the tested compounds for 9 days twice daily, the decrease in BP persisted for at least 16 h after the last dose. Proxyphylline produced the most marked decrease in diastolic and mean BP. Among the xanthines examined, proxyphylline nitrate had the strongest hypotensive effect when administered in a single dose to animals pretreated with the same compound for 9 days. These results indicate that insertion of a nitrate group weakly modifies the hypotensive action of the studied xanthines in SH rats.

A new nitrate derivative of piperazine: its influence on platelet activity.

Nitric oxide (NO) is a potent vasodilator and inhibitor of platelet activation. Its donors, organic nitrates, are still a main group of drugs administered in ischaemic heart disease. The aim of this study was to investigate the effect of a new NO-donor analogue, 1-(3-piperidinepropionyl)-4-(2-nitrooxy-3-piperidinepropyl) piperazine trihydrochloride (NO-P), on platelet activity. Its influence on the main mechanisms of human platelet activation (adhesion, shape change, secretion and aggregation) was evaluated with the use of a pharmacological model produced on the basis of known platelet activation measuring methods and our computer program. Our experiments revealed that the new NO derivative of piperazine favourably influences platelet activity, and decreases adhesion (spontaneous and induced by ADP) and aggregation. NO-P shows the same direction of action as nitroglycerin (used as a model compound), and is even stronger in the case of ADP-induced and collagen-induced aggregation. These findings broaden the possibility of using NO-P in cardiovascular diseases. Furthermore, our computer program, used to evaluate kinetic parameters of platelet aggregation, shape change, and the adhesion measuring method, provides a simple and accessible experimental model. This model can be useful in in-vitro screening studies, estimating the influence of new compounds (potential drugs) on platelet activity.

Study on organic nitrates, part VIII. Pharmacological activity and nitric oxide generation capacity of nitrate derivatives of piperazine.

Organic nitrates, derivatives of piperazine, incubated with L-cysteine hydrochloride in phosphate buffer at appropriately high pH and temperature underwent decomposition, releasing nitric oxide (NO). NO generated in this reaction was quantitated by polarographic method using a selective ISO NO sensor. Spontaneously hypertensive rats were used in the tests of hypotensive activity of both investigated organic nitrates and their hydroxyl analogues. The experiments with both groups of compounds were performed under identical conditions. The results of the study demonstrated that the ability of individual compounds to release NO influenced in a different manner their pharmacological activity. Only the compound which released the largest quantity of NO during in vitro tests exhibited in vivo the most prolonged hypotensive effect and significant decrease in all arterial blood pressure parameters.

The study on organic nitrates, part V. New derivatives of piperazine potential NO donors.

We have obtained a series of non-symmetrical 1,4-disubstituted derivatives of piperazine, with the structure of organic nitrates, as potential NO donors. These compounds were obtained from respective hydroxyl derivatives of piperazine in an esterification reaction by fuming nitric acid. The obtained nitrates were tested in-vitro by reaction with a sulfhydryl compound. The structure of the most active nitrate and its hydroxyl analogue was used for the calculation of geometrical optimization with the determination of 3D-QSAR by a semi-empirical method PM3 using HyperChem 4.5.

A study on organic nitrates, Part VI. Synthesis and pharmacological activity of 1-isopropylamino-3-(1-naphthyloxy)-2-propyl nitrate.

Basing on the studies on the relationship between the structure and activity, we have synthesized a nitrate analogue of propranolol as potential donor of nitric oxide. The obtained 1-isopropylamino-3-(1-naphthyloxy)-2-propyl nitrate decreases blood pressure more than propranolol and slows the heart rate less than propranolol. It also affects peripheral vascular resistance less than propranolol.