Extraction of pharmaceutically active components from plant materials

1. A method of extracting cannabinoids from plant material comprising a decarboxylation step, an extraction with liquid carbon dioxide (CO 2 ), and a step to reduce the proportion of non-target materials in the extract, characterised in that the extraction with liquid CO 2 is conducted under sub-critical conditions at a temperature in the range of from 5 to 15° C. and a pressure in the range of from 50 to 70 bar.

2. A method as claimed in claim 1 wherein the decarboxylation step is carried out after extraction with liquid CO 2 .

3. A method as claimed in claim 1 wherein the decarboxylation step is carried out prior to extraction with liquid CO 2 .

4. A method as claimed in claim 1 wherein the temperature is in the range of from 8 to 12° C.

5. A method as claimed in claim 1 wherein the pressure is in the range of from 55 to 65 bar.

6. A method as claimed in claim 1 wherein the CO 2 has a mass flow in the range of 1000–1500 Kg/h.

7. A method as claimed in claim 1 wherein the extraction is run for up to 10 hours.

8. A method as claimed in any of claims 1 – 4 , 5 , 6 and 7 wherein the CO 2 is removed by depressurisation and the recovered extract held at a temperature in the range from −15° C. to −20° C.

9. A method as claimed in claim 1 wherein the step to reduce the proportion of non-target materials in the extract is a precipitation with a C1–C5 alcohol, wherein the material to be treated is warmed to above room temperature before the C1–C5 alcohol is added.

10. A method as claimed in claim 9 wherein the C1–C5 alcohol is ethanol.

11. A method as claimed in claim 9 wherein the extract is warmed to a temperature in the range from 36° C. to 44° C.

12. A method as claimed in claim 10 wherein the C1–C5 alcohol is added in an amount of from 3:1 to 1:1 C1–C5 alcohol volume to weight of the material to be treated.

13. A method as claimed in claim 9 wherein the solution resulting from addition of C1–C5 alcohol to the material to be treated is chilled and insoluble materials allowed to precipitate out.

14. A method as claimed in claim 13 wherein the solution resulting from addition of C1–C5 alcohol to the material to be treated is chilled to a temperature in the range from −15° C. to −25° C.

15. A method as claimed in claim 13 wherein the precipitate of insoluble materials is removed by filtration.

16. A method as claimed in claim 9 further comprising a multi-step evaporation under reduced pressure.

17. A method as claimed in claim 16 wherein the first C1–C5 alcohol is removed and then water is removed.

18. A method as claimed in claim 3 wherein the decarboxylation step is carried out prior to extraction with liquid CO 2 and is conducted by heating the plant material to temperatures and for times which ensure at least 95% conversion of the acid cannabinoids to their neutral form whilst ensuring thermal degradation of THC to CBN is less than 10%.

19. A method as claimed in claim 18 in which a multi step heating process is conducted in which the plant material is:

i) heated to a first temperature for a first time period to evaporate off retained water and allow for uniform heating of the plant material; and

ii) the temperature is increased to a second temperature for a second time period until at least 95% conversion of the acid cannabinoids to their neutral form has occurred.

20. A method as claimed in claim 1 further comprising the step of treating an extract derived from the plant material with activated charcoal.

21. A method of making a pharmaceutical composition comprising, as an active agent, a botanical drug substance which is an extract from at least one cannabis plant, which method comprises preparing a botanical drug substance containing cannabinoids from at least one cannabis plant using an extraction method according to claim 1 , and formulating the botanical drug substance with one or more pharmaceutically acceptable diluents, carriers or excipients to produce a pharmaceutical composition.