Inhibitory effect of 3-carboethoxypyridine and 3-carbobutoxypyridine on isolated rat uterus.

3-Carbomethoxypyridine (CMP) was isolated and characterized from the leaves of Pyrenacantha staudtii Hutch and Dalz, family Icacinaceae, in our earlier study and was found to possess an inhibitory activity on the isolated rat uterus. In order to study the structure - activity relationship, derivatives of CMP were obtained synthetically, purified and characterized by spectroscopic techniques such as infra red spectroscopy (IR), nuclear magnetic resonance (1H- and 13C-NMR) and mass spectrometry (MS). The synthesized compounds were subjected to pharmacological testing using isolated rat uterine preparation in oestrus suspended in an organ bath containing De Jalon physiological salt solution (PSS). The force of contraction was recorded via an isometric transducer connected to an Ugo Basile recorder. The effects of these two compounds were compared with salbutamol as a positive control. 3-Carboethoxypyridine (ECP) demonstrated very significant (p < 0.005) inhibitory activity on the uterus with a total elimination of the spontaneous contractility at a dose of 0.4 mg/mL. Carbobutoxypyridine (BCP) also demonstrated a marked reduction of oxytocin-induced contractions and elimination of spontaneous activity. The study lends support to the potential use of these agents as tocolytics.