Methods of purifying cannabinoids using liquid:liquid chromatography
The present specification discloses methods of purifying one or more cannabinoids from a plant material using unique biphasic solvent systems and liquid-liquid chromatography as centrifugation partitioning chromatography (CPC) or counter current chromatography (CCC). The present specification also provides purified cannabinoids such as CBG, CBGA, CBGV, CBD, CBDA, CBDV, THC, THCA and THCV, compositions comprising one or more of these cannabinoids produced by the disclosed method, and methods for treating a disease or condition employing such purified cannabinoids and compositions.
1. A method of purifying one or more cannabinoids from a plant material including a plant, a plant resin or a plant extract, the method consisting essentially of the following steps:
(a) incubating the plant material with a solvent selected from the group consisting of pentane, hexane, heptane, petroleum ethers, cyclohexane, dichloromethane, trichloromethane, tetrahydrofuran, diethyl ether, toluene, benzene, ethanol, methanol, isopropanol, acetone, acetonitrile, ethyl acetate, butane, propane, 1,1,1,2-Tetrafluoroethane (R134a) or, liquid, subcritical or supercritical CO 2 or mixes thereof to form a solvent mixture which extracts the one or more cannabinoids from the plant material, wherein the solvent mixture has an original volume;
(b) for THC-type extracts, adding to the solvent mixture a biphasic solvent system selected from the group consisting of hexane:ethanol:water, pentane:acetonitrile and hexane:acetonitrile, wherein the pentane:acetonitrile system and the hexane:acetonitrile system optionally include ethyl acetate and/or water as a modifier; for CBD-type extracts, adding to the extract a biphasic solvent system of hexane:ethanol:water; and for CBG-type extracts, adding to the extract a biphasic solvent system of hexane:ethanol:water; and
(c) performing liquid:liquid chromatography using a biphasic solvent system of step b), thereby purifying the one or more cannabinoids,
wherein fractions of tetrahydrocannabinol (THC) contaminated by cannabichromene (CBC) or fractions of tetrahydrocannabivarin (THCV) contaminated with cannabinol (CBN) are re-purified using solid-liquid chromatography selected from the group consisting of gravity, Flash or preparative HPLC over C-8 or C-18 coated silica solid stationary phase, using a gradient of acetonitrile:water mobile liquid phase.
2. The method of claim 1 , wherein for the THC-type extracts the biphasic solvent system is hexane:ethanol:water is at a ratio of (20:17:3) by volume.
3. The method of claim 1 , wherein for the THC-type extracts the biphasic solvent system is pentane:ethyl acetate:acetonitrile:water or hexane:ethyl acetate:acetonitrile:water at a ratio from (10:0:10:0) to (7:3:7:3) by volume.
4. The method of claim 1 , wherein for the CBD-type extracts the biphasic solvent system is hexane:ethanol:water at a ratio of (20:14:6) by volume.
5. The method of claim 1 , wherein for the CBG-type extracts the biphasic solvent system is hexane:ethanol:water at a ratio of (20:12:8) or (20:13:7) by volume.
6. The method of claim 1 , wherein an extract of chemotype I or II Cannabis sativa L. is used to purify THC, THCA, THCV, THCVA, CBN or CBV and fractionate the CBD-type and CBG-type cannabinoids.
7. The method of claim 1 , wherein an extract of chemotype II or III Cannabis sativa L. is used to purify CBD, CBDA, CBDVA or CBDV and fractionate the THC-type and CBG-type cannabinoids.
8. The method of claim 1 , wherein an extract of chemotype IV Cannabis sativa L. is used to purify CBG, CBGA, CBGVA or CBGV and fractionate the CBD-type and THC-type cannabinoids.
9. The method of claim 1 , wherein the liquid:liquid chromatography is centrifugation partitioning chromatography (CPC) or is counter current chromatography (CCC).
10. The method of claim 1 , wherein after step a) the solvent mixture is reduced to dryness or to about 50% or less of the original volume of the solvent mixture in step (a) thereby concentrating the one or more cannabinoids before the liquid:liquid chromatography.
11. The method according to claim 1 , wherein the solvent mixture of step (a) is purified prior to step (b).
12. The method according to claim 1 , wherein prior to step (a), the one or more cannabinoids present in the plant material are decarboxylated by heating the plant material.
13. The method of claim 10 , wherein after the solvent mixture is reduced to dryness, a dry extract product of the solvent mixture is dissolved in ethanol, chilled at a temperature from −20° C. to 4° C., filtered to remove precipitated material and reduced to dryness before purification by liquid-liquid chromatography.
14. The method of claim 9 , using a rotor design Quantum CPC or CPC PRO, wherein the total run time is 12-20 minutes, independent of rotor volume.
15. The method of claim 7 , wherein the CBD, CBDA, CBDVA or CBDV is crystalized after the step of liquid:liquid chromatography.
16. The method of claim 8 , wherein the CBG, CBGA, CBGVA or CBGV is crystalized after the step of liquid:liquid chromatography.
17. The method of claim 1 , wherein in step (a) the plant material is incubated with a non-polar solvent selected from the group consisting of petroleum ether, pentane, hexane and heptane to form a solvent mixture which extracts the one or more cannabinoids from the plant material to form the solvent mixture.
18. The method of claim 1 , wherein the plant material is first incubated with a solvent selected from the group consisting of pentane, hexane, heptane, petroleum ethers, cyclohexane, dichloromethane, trichloromethane, tetrahydrofuran, diethyl ether, toluene, benzene, ethanol, methanol, isopropanol, acetone, acetonitrile, ethyl acetate, butane, propane, 1,1,1,2-Tetrafluoroethane (R134a) or, liquid, subcritical or supercritical CO 2 or mixes thereof; filtered, decanted or centrifuged; reduced to dryness; and then incubated with a non-polar solvent selected from the group consisting of petroleum ether, pentane, hexane and heptane to form a solvent mixture which extracts the one or more cannabinoids from the plant material to form the solvent mixture.
19. The method of claim 14 , wherein the rotor has a rotor volume of 1 liter, a sample injection of 50 mL, a flow rate of a mobile phase (pentane or hexane phase) of the biphasic solvent system of 200 mL/min during the run, and a flow rate of a stationary phase (the ethanolic or acetonitrile phase) of the biphasic solvent system of 350 mL/min during the extrusion phase of the run.