CO2-Soluble GRAS Solvents for Extracting Nutraceuticals
By a Gas Anti-Solvent (GAS) Process
Peter K. Kilpatrick, Ruben G. Carbonell
Graduate Student Mentors: Xenia Tombokan and Remil Aguda
Department of Chemical and Biomolecular Engineering
North Carolina State University, Raleigh, NC 27695
This project involves a novel extraction process for obtaining high value
nutraceuticals from plants. It utilizes CO2-soluble GRAS (generally recognized as safe)
ester solvents to extract the nutraceuticals from plant tissues. CO2 is then used to recover
the product via a gas anti-solvent (GAS) process1,2. This is followed by an increase in
pressure to dissolve and recycle the liquid solvent. Since the liquid extraction step, the
GAS process, and the dissolution of the liquid solvent can all operate at ambient
temperatures, this process can reduce product degradation and thus increase yields.
Current work focuses on screening for the GRAS solvents that give the best solubility for
nutraceuticals (yield) and on finding the best conditions to optimize product yields and
purity (selectivity).
Nutraceuticals are polar organic molecules extracted from plants which have
associated health benefits. As model systems, we are studying the recovery of
anthocyanins isolated from purple sweet potato, solanesol and sclareol isolated from clary
sage, and lutein as well as zeaxanthin derived from marigold flowers. The first approach
to this project is to screen for GRAS solvents that can effectively remove these materials
from plant tissues. Alkyl aryl esters are promising for this purpose since their substituent
groups can be chosen to achieve desired polarity and hydrophobicity to target a specific
product. In addition, complete miscibility of these esters with dense CO2 makes them
suitable for GAS precipitation.
Screening of GRAS solvents is done by measuring the solubility of each solute of
interest in various ester solvents. Measurements can be done using UV visible
spectroscopy for anthocyanins and marigold derivatives. However, it is difficult to
analyze sclareol and solanesol using this method because they have very low absorbance
at visible ranges of wavelengths. Hence, gas chromatography is used to measure the
solubility of these components. We plan to extend our work in this project to optimize the
extraction and fractionation of lutein and zeaxanthin using alkyl alkyl esters. These
important are critical for controlling the health and vitality of important tissues in the eye
for sight.
References
1. Liu, Z.; Li, D.; Yang, G.; Han, B. (2000). Solubility of hydroxybenzoic acid
isomers in ethyl acetate expanded with CO2. Journal of Supercritical Fluids
18:111-119.
2. Cocero, M.J.; Ferrero, S. (2002). Crystallization of β-Carotene by a GAS
process in batch: Effect of operating conditions. Journal of Supercritical
Fluids 22: 237-245.
3. Chang, C.J.; Randolph, A.D.; Craft, N.E. (1991). Separation of β-Carotene
Mixtures Precipitated from Liquid Solvents with High-Pressure CO2.
Biotechnology Progress 7: 275-278.
4. Catchpole, O.J.; Hochmann, S.; Anderson, S.R.J. (1996). Gas Anti-Solvent
Fractionation of Natural Products. High Pressure Chemical Engineering,
Industrial Research Ltd.