DETERMINATION OF HYDROLYSIS PARAMETERS OF YOHIMBINE HCl AT NEUTRAL AND SLIGHTLY ACIDIC MEDIUM
Journal Title: International Journal of Pharmacy and Pharmaceutical Sciences - Year 2015, Vol 7, Issue 5
Abstract
Objectives: In the process of investigating various new drug delivery systems of yohimbine HCl (Yoh), it was necessary to study some of the physical chemical properties of the drug including its stability at neutral, acidic and slightly acidic conditions.Methods: A validated HPLC method was developed and employed for analysis of Yoh containing solutions. The mobile phase composed of 60% menthol: 40% NaOAc (%v/v), and Gemi C18 column, 5 µm particle size was used as a stationary phase. The degradation product was found to be yohimbinic acid (YA). The retention times for Yoh and YA were 5 and 3 minutes, respectively. This study investigated the kinetics of hydrolysis of Yoh at pH 6.0 and 7.0 at temperatures from 50 °C to 80 °C.Results: The reaction followed first order kinetics and the activation energy ∆E of the reaction at pH 6 and pH 7 was found to be 16.2 and 16.8 Kcal. mole-1, respectively. While the values of A were found to be 41.8 and 44.1 Kcal. mole-1 at pH 6 and 7, respectively. The pseudo first order rate constants (K) at pH 6 and 7 were calculated as 2.76 Ñ… 10 -3 h-1 and 3.42 Ñ… 10 -3 h-1, respectively.Conclusion: Such results indicate high stability of the drug at these pH values. At highly acidic medium the reaction was found to be extremely slow indicating the absence of acid catalysis on the hydrolysis of Yoh. Thus, the yohimbine ester group resists hydrolysis in highly acidic conditions.Â
Authors and Affiliations
Riad Awad, Eyad Mallah, Faisal Al-akayleh, Tawfiq Arafat, Bayan Alkhawaja, Kenza Mansoor, Wael Abu Dayyih
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