Author Topic: THC: alkaline wash of hemp extract  (Read 1140 times)

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THC: alkaline wash of hemp extract
« on: December 25, 2003, 10:08:00 PM »
As it seems impossible to enter a reply into an already existing forum I´m obliged to start a new thread:
O.K. Ma_Huang here goes the answer to your question:
A petrol ether extract (soak 1hr at room temp., pour off, repeat) of not too old hemp will consist mostly out of cannabinoid acids, such as THC-acid and CBD-acid, depending on the strain one is working with.
These cannabinoid acids can be brought into aqueous solution as alkali salts by washing the petrol-ether extract with dilute KOH for instance (0.1molar  KOH with some Na2SO3 thrown in just in case this prevents some oxidation).
Acidification of the aqueous extract and extraction with petrol ether will yield (after washing excess acid away) upon careful evaporation on a water bath (60° centigrade is possible) in the vacuum an oily to glass-like residue, which consists, depending on the strain of hemp one is working with and the quality of the material (seedless?) up to ca 90% out of THC-acid(s).
This will give THC of similar purity upon decarboxylation (heat up to 150° centigrade under vacuum – careful! Foaming! Product sensitive to oxidation).
The initial petrol ether extract of the hemp will (after it has been extensively washed with dilute alkali, excess alkali been removed with dilute citric acid and finally washed with water) yield the neutral cannabinoids, as far as they have been present in the plant material, along with other lipophilic materials.
CBN will still be largely in this "neutral" fraction as the high lipophilicity of cannabinoids  hardly allows the purely phenolic materials to form any water-soluble salts on treatment with dilute alkali.
Grass that has been sitting in the dark at room-temperature for 2 years may have about ½  of its original THC-acid content decarboxylated. About 1/3 of the THC  may have oxidized to CBN in the same time.
Choice of solvent for extracting hemp:
More polar organic solvents will also extract cannabinoids but also more non-cannabinoids.
The aqueous extraction of cannabinoid acids with dilute alkali works only really well with hemp extracts in non-polar solvents.
Be aware that THC is extremely sensitive to oxidation when it is dissolved in petrol ether or other lipophilic solvents (an exception maybe the solution in fats/vegetable oil, which is quite stable) .
Work fast and avoid high temperature!
Anecdotal reports about bioassays of oxidized material show this material to cause bad headache.
An alcohol extract of hemp will be much more stable and the danger of unwanted oxidation of  THC to CBN is greatly reduced, but you will end up with a far less pure product.


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CBN and alkali extraction
« Reply #1 on: December 26, 2003, 01:53:00 PM »
Merck index (12th edition) states that cannabinol (CBN) is soluble in aqueous alkali.
In my post above I wrote that CBN remains largely in the petrol ether phase.
Now how does this go together?
Well, Merck index makes this claim surely for pure CBN and doesn´t give any figures as to how much is soluble in aq. alkali.
In the extraction as discussed above we are dealing with a distribution equlibrium between CBN dissolved in petrol ether and an alkaline aq. phase.
This is something different because we have to take the net energy of the steps into account, that are necessary to get the CBN from one phase into the other.
Remember also we are dealing here with an extract of natural material rich in phase transfer catalysts and solubility facilitators. So the picture is indeed far more complex.
But indeed after two extractions  with aq. alkali CBN remained largely in the petrol ether phase and only some was found the water.


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THC: alkaline wash of hemp extract
« Reply #2 on: December 31, 2003, 02:49:00 AM »
All good information, thanks.

Regarding the solubility of CBN, maybe the Merck has got CBN and CBNA confused? It wouldn't be the first time. I am still harbouring ambitions of reducing CBN -> THC (or maybe even further), and I guess the main question is whether or not I have to muck around with fancy procedures like catalytic hydrogenation, Birch reductions, etc. Prior to your posting, I had been trying to think of something simple that might work in alkaline conditions, like maybe H2S. But now with an organic co-solvent, Na2S2O5 and acidic conditions could still be worth a try.

For the record, I can see that my original idea of investigating halogenation for potentially greater potency is probably a dud. Use of Br2 or I2 would certainly oxidise THC before it did anything else. It's hard to say what might happen with HBr/HI.