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Betulinic, oleanolic and ursolic acids are naturally occurring triterpenic acids that have attracted considerable interest due to their nutraceutical and pharmacological properties. These compounds can be extracted from natural sources, however, their simultaneous occurrence and very similar structures make their separation a challenging task. In this work we designed a simulated moving bed (SMB) unit for the separation of a representative natural extract containing betulinic, oleanolic and ursolic acids into high purity compounds using a two-step process: firstly, betulinic acid was isolated from oleanolic and ursolic acids, and secondly oleanolic and ursolic acids were fractionated. Preliminary HPLC experiments were conducted to select appropriate mobile and stationary phases. Equilibrium and mass transport parameters were determined through breakthrough experiments with pure compounds in a single column. Subsequently this information was successfully applied in the simulation of a ternary mixture separation, whose results were validated with ternary breakthrough measurements. Finally, the SMB was designed and optimized using a Design of Experiments approach combined with Response Surface Methodology (DoE-RSM), and simulated using a phenomenological rigorous model. It was concluded that using the designed SMB unit it is possible to produce betulinic, oleanolic and ursolic acids with purities of at least 99.4%, 99.1%, and 99.4% (all mass fraction), from a feed mixture containing 20%, 25%, and 55% of each acid, respectively. [ABSTRACT FROM AUTHOR]

SFE curves of Eichhornia crassipes are measured for different pressure (200, 250, and 300 bar), ethanol content (0 and 5 wt.%), and CO 2 flow rate (5.0, 7.5 and 10.0 g min −1 ) conditions, and studied in terms of total ( η total ) and stigmasterol ( η stigm ) extraction yields. Ethanol addition was able to increase total yield up to 60% within the 6 h of extraction, reaching up to η total = 1.25 (wt.%). For stigmasterol uptake, two yield plateaus were observed within the six runs: one at η stigm = 0.17 (wt.%) for 0.0 (wt.%) ethanol and the other at 0.23 (wt.%) for 5.0 (wt.%) ethanol, which suggests that the attainable practical amount of extractives depends on whether cosolvent is used or not. Simplified modeling disclosed that both intraparticle diffusion and film diffusion may be present in the SFE process. On the other hand, the broken plus intact cells (BIC) model of Sovová allowed to fit experimental data with deviations of 4.20% for η total and 4.02% for η stigm , and to get instructive insights on the process. In fact, BIC model evidenced the existence of a selectivity advantage favorable to stigmasterol that is driven by kinetics rather than by solubility, which is corroborated by the fact that shorter extraction periods were noticed in stigmasterol yield curves than in the global extract yield curves. In the whole, these results and insights support the realization of scale-up assays and provide a contribution for the valorization of water hyacinth through a green process devoted to the production of stigmasterol enriched extracts. [ABSTRACT FROM AUTHOR]

• SFE of friedelin from Quercus cerris cork with pure/modified CO 2. • Experimental conditions tested: 40–60 °C, 0–5 wt% ethanol, 5–11 g C O 2 m i n - 1 . • Optimization of the SFE following DoE and RSM approaches. • Total yield, friedelin concentration and selectivity to friedelin were measured. Optimization of the supercritical fluid extraction of Quercus cerris cork was carried out using Box-Behnken design of experiments and response surface methodology (RSM). The optimized process variables were temperature (T : 40, 50 and 60 °C), ethanol content (EtOH: 0.0, 2.5 and 5.0 wt%) and CO 2 flow rate (Q C O 2 : 5, 8 and 11 g m i n - 1 ). The studied responses were total extraction yield (η T o t a l), friedelin concentration of the extract (C F r i e d e l i n), and selectivity towards friedelin (α F , n F). The linear effect of EtOH was by far the most influent operating condition (Pareto analysis) and the highest yield (η T o t a l = 2.2 wt%) was attained with 5.0 wt% EtOH. The RSM model estimates maximum friedelin concentration in the extracts (38.2 wt%) to occur without cosolvent (0 wt% EtOH) for the lowest T (40 °C) and Q C O 2 (5 g C O 2 m i n - 1 ). As for selectivity, the experimental α F , n F values were always higher than 1.0 and reached 3.1 (at 50 °C, 5 wt% EtOH, 11 g C O 2 m i n - 1 ). Altogether, these results suggest friedelin can be selectively removed from Quercus cerris cork by supercritical fluid extraction within the range of experimental conditions studied. [ABSTRACT FROM AUTHOR]

• 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]