Carnosol purification. Scaling-up centrifugal partition chromatography separations

- Carnosol is an active pharmaceutical principle found in rosemary.
- The purification method is optimized on a small centrifugal partition chromatography column (CPC).
- To be quickly transferred on larger CPC instruments using the recently proposed “free space between peaks” method.

This paper illustrates the application of a recently proposed protocol allowing the scale-up prediction on hydrostatic countercurrent chromatography columns (centrifugal partition chromatographs or CPC). A commercial extract of rosemary (Rosmarinus officinalis L.) was used as the starting material containing 0.48% of carnosol, an active pharmaceutical ingredient with great potential. After a rapid method development on a small-scale 35-mL CPC instrument that allowed for the determination of the solvent system and maximum sample concentration and volume, the purification was transferred on two larger instruments using the “free space between peaks” method. The method takes into account the technical limitations of the larger instruments, such as pressure and/or maximum centrifugal field, and allows, by simply running an analytical-sized injection on the large scale rotor, to give an accurate prediction of the maximum sample load and best throughput. The 0.27 g of rosemary extract maximum load on a 35-mL CPC was transferred as a 1.9 g load on a 254-mL medium size CPC and 9 g load on a 812-mL CPC. The maximum process efficiency of 3.1 mg of carnosol per hour obtained on the small 35-mL column was transferred on the 254-mL CPC giving 8.3 mg/h and, on the larger 812-mL column 49.4 mg of carnosol could be obtained per hour. If the scaling-up in CPC instruments is not directly homothetic, it can be highly predictable through a few simple experiments.