Chromatographic separation of betulinic and oleanolic acids.

• Design an SMB unit for the separation of mixtures of betulinic and oleanolic acids. • Selection of mobile and stationary phases by elution chromatography assays. • Determination of equilibrium and mass transfer parameters via breakthrough experiments. • Optimization of the SMB operation using statistical methods and computer simulations. • The two compounds can be obtained with purities above 99% using the optimized SMB. In this work, a simulated moving bed unit (SMB) was designed for the separation of betulinic and oleanolic acids, two naturally occurring triterpenic acids that exhibit key pharmacological properties. Preliminary impulse experiments were conducted to select appropriate mobile and stationary phases, from which methanol/acetonitrile 50/50 (%, v/v) and an Apollo C18 column emerged as the most favorable option. Breakthrough experiments were conducted with the pure compounds to determine the equilibrium and mass transfer coefficients necessary for SMB simulations. These parameters were then validated through the successful prediction of breakthrough experiments of two binary mixtures of betulinic and oleanolic acids. Optimum SMB operating conditions were determined via an optimization strategy combining the design of experiments and response surface methodologies (DoE-RSM) with phenomenological computer simulations. It was demonstrated that an SMB unit consisting of two columns per section allows the recovery of betulinic acid in its raffinate stream with a purity of 99.0 % and oleanolic acid in the extract stream with 99.4 % purity. Moreover, it was also demonstrated that the addition of acetonitrile to methanol is translated into a gain of 16.1 % in terms of productivity when compared to other mobile phase such as methanol/water 95/5 (%, v/v). [ABSTRACT FROM AUTHOR]