Complexation, Stability and Stoichiometry of Iron (III) with Salbutamol (Active ingredient of Asthma drug Ventolin®)

Asthma is a wide speared disease all over the world. In this disease breathing is not smooth due to contraction of bronchitis. Ventolin is an effective drug for this purpose and is widely used. Its active ingredient is Salbutamol Sulphate, which is bronchodilator. Due to oxygen and nitrogen donor sites of Salbutamol (Fig I), it has been assumed that it may interact with metals present in the biological system, and therefore disturb the metals metabolism and imbalance the equilibrium. On the other hand two third of the body’s iron is found in hemoglobin which is an oxygen storage protein. Therefore may iron is chelated by the Salbutamol ion in the stomach. The chelation of iron by salbutamol, stability of the complex and Stoichiometry at acidic pH of the said complex is investigated implied Spectrophotometric technique. Salbutamol formed highly colored complex with iron having maximum absorbance at 550nm. A 1:3 complex formation in buffered and non buffered solutions at 30°C was found using mole ratio and slope ratio methods. Molar extinction coefficients were determined by calibration curve method and was found very high in non buffered solution comparative to buffered solutions. Stability constant of ML1 is found 6.3635, ML₂ is 11.919 and ML3 is 16.858 in non buffered solution. Closer ln values were found in buffer of pH 3.0 and 3.5.