The isolation of ricinoleic acid from castor oil by salt-solubility-based fractionation for the biopharmaceutical applications

The goal of this work was to develop a method for the preparative isolation of ricinoleic acid (RA) from Castor oil (CO) for use as building blocks in biopharmaceutical synthesis. The separation efficiency achieved with the impurity extraction approach (IEA) and the salting-out approach (SOA) based on utilization of monobasic alkali salt of RA was examined. SOA showed better separation efficiency. Fractional precipitation from the co-solvent system consisting of isopropyl ether:ethanol (IPE:EtOH) 65:35 v/v and applied at a CO: co-solvent system mass: volume ratio of 1:5 produced a high quality purified RA (purity 97.9-98.6%). It contains residuals of linoleic acid and oleic acid as the main impurities and satisfies all requirements of the official compendia for oleaginous vehicles for parenteral administration. The total yield of this process was 55.5 ± 2.5% and the recovery of RA was about 70% (calculated relatively to the yield of the crude product). The study of the synthesis kinetics of RA oligomers and of the biopolymer prepared from these oligomers indicated that mono-functional fatty acids (FAs) affect the composition of the oligomers' mixture and delay chain elongation of both RA oligomers and biopolymer. The developed novel process is simple, flexible, highly reproducible, inexpensive, and has high scalability potential.