Extraction and purification of cannabinoids
An improved method for making cannabinoids from plant material utilizes the following steps. Plant material is contacted with an aqueous alkaline solution containing a hydroxide base and essentially no organic solvents, thereby extracting cannabinoids including carboxylic acids and salts and producing an alkaline extract. Non-soluble plant material is removed from the alkaline extract to produce a clarified alkaline extract. The extracted cannabinoids are decarboxylated and the decarboxylated cannabinoids are crystallized/precipitated from the clarified alkaline extract at a pH greater than 7.
1. A method for purifying cannabidiol from cannabis , the method comprising:
a. contacting cannabis with an aqueous alkaline solution of a strong inorganic base selected from the group consisting of NaOH, KOH, NH 4 OH, and combinations thereof, to extract cannabidiolic acid from the cannabis and produce an aqueous alkaline extract of cannabis , wherein no organic solvents are used;
b. purging the aqueous alkaline extract of cannabis with an inert gas selected from the group consisting of nitrogen, argon, helium, and combinations thereof to produce a purged aqueous alkaline extract of cannabis;
c. removing non-soluble material from the purged aqueous alkaline extract of cannabis via filtration, centrifugation or both to produce a clarified extract of cannabis;
d. decarboxylating the clarified extract of cannabis at a temperature sufficient to convert the cannabidiolic acid to cannabidiol;
e. crystallizing and precipitating the cannabidiol from the clarified extract at a pH greater than 7 to produce crystallized and precipitated cannabidiol;
f. filtering the crystallized and precipitated cannabidiol to produce 85% to 100% cannabidiol and a barren aqueous solution of the strong inorganic base; and
g. recycling and reusing the barren aqueous solution of the strong inorganic base from step (f) and then extracting new cannabis with the barren aqueous solution of a strong inorganic base selected from the group consisting of NaOH, KOH, NH 4 OH, and combinations thereof.
2. The method of claim 1 , wherein the cannabis is not dried prior to step (a).
3. The method of claim 1 , wherein the cannabis is hemp.
4. The method of claim 1 , wherein the strong inorganic base is NaOH.
5. The method of claim 1 , wherein the step (c) of removing non-soluble material from the purged aqueous alkaline extract of cannabis to produce a clarified extract of cannabis is performed using centrifugation.
6. The method of claim 1 , wherein the crystallizing and precipitating of the cannabidiol from the clarified extract is performed at a pH greater than 9 to produce the crystallized and precipitated cannabidiol.
7. The method of claim 1 , wherein the inert gas is nitrogen.
8. The method of claim 1 , wherein the clarified extract of cannabis is heated to a temperature in a range of from about 35° C. to about 75° C. to increase the rate of decarboxylation in step (d).
9. The method of claim 1 , wherein the step (d) of decarboxylating and step (e) of crystallizing and precipitating occur at a pH range of about 12 to about 13.5.
10. The method of claim 1 , wherein no acid is added to the clarified extract of cannabis.
11. The method of claim 1 , wherein the barren aqueous solution of the strong inorganic base is filtered using an alkaline tolerant nanofiltration membrane prior to step (g).
12. The method of claim 1 , further comprising washing the 85% to 100% cannabidiol from step (f) with water purified by reverse osmosis.
13. The method of claim 1 , wherein the aqueous alkaline solution of a strong inorganic base is initially prepared using water purified by reverse osmosis.