couldntthinkofaname - 14-9-2015 at 17:18
I am attempting to extract certain alkaloids from green plant matter (very high in waxes and fats)
I understand that in this scenario it is common to first acidify and us NP solvent to defat the solution.
I am curious though: say I were to basify and extract alkaloids without any defatting. If I were then to add HCL solution to the NP solvent which now
contains the alkaloids, wouldn't this in theory be equivalent to the defatting stage? Wouldn't the alkaloids would now be in the aqueous layer, and
the lipids would be stuck in the NP layer?
As the a/b method is so common, I am wondering if there are any downsides to the method described above that I am unaware of. I only have enough
material for one shot so I would just like to hear some input before I attempt this expedited method.
May main fear would be emulsions that wouldn't break up. Is this a valid concern that is remedied by a preliminary defatting stage? Are there other
concerns I should be wary of?
Ozone - 14-9-2015 at 18:18
Yes. Another name for the traditional scheme is A/BN or acid and base/neutral. Acidifying first renders the bases into soluble salts (aq) and doesn't
effect neutral waxes. Fatty acids are protonated into free-acid form--which is least soluble (aq). The first extraction thus removes neutrals and
acids.
If you go the other way, your waxes and fatty acids (to some extent) will be extracted with your bases.
So, unless you want to do column clean up (florisil works well), I'd proceed A/BN.
edit: If you intend to crash the salt, it will probably work. But--your solvent capacity may be shot if there is a lot of (as you say) wax. It will be
preferentially (depending on solvent) soluble over most soluble organic free bases. I'd predict that your recovery will be much lower this way.
Washing the wax-laden solvent from your product will also certainly cost you some yield on recovery. I imagine this could be improved by using a lot
more solvent (or more extraction stages), but that is something I generally try to avoid.
O3
[Edited on 15-9-2015 by Ozone]
couldntthinkofaname - 14-9-2015 at 19:38
Thanks for the info.
Just out of curiousity, once one the final basification stage, does the freebased alkaloids immediatly migrate to the solvent or should they be left
to sit for a period of time?
Ozone - 14-9-2015 at 19:49
Look up liquid-liquid extraction (more applicable to A/BN) and the Craig counter-current apparatus. See, also (solid-liquid extraction, for plant
matter), Soxhlet apparatus and then column chromatography. Learn the fundamentals first.
Might as well make it educational.
[Edited on 15-9-2015 by Ozone]
Pumukli - 15-9-2015 at 11:28
Doing defatting before extraction may have an advantage: one can remove possible emulgeators. In the next extraction step it can be nice.
Have you tried extracting (A/B) something from an emulsion? It can be messy.
Ozone - 15-9-2015 at 19:37
That's another reason why acidifying a liquid (not a solid, like this) first is a good idea: emulsifying protein will ppt as well. Filter that out and
then pull the BNs out.
And, yes. Do not try to extract milk with hexanes before crashing out the protein...
O3
[Edited on 16-9-2015 by Ozone]
Willsolvem - 19-11-2015 at 16:39
I have some plant material also very high in fat like garbage. I prefer washing an aq than defatting the plant material directly. My soxhlet has
about an 80g capacity making the use of largeramounts arduous at best.
Here's my problem:
On the first few pulls with a np a heavy, honey colored and with a simular consistency fats remain after the removal of solvent. Subsequent pulls
leave a lighter oil, simular to baby oil in consistency and color on removal. These latter oils require high volumes of solvent to be removed. And as
it be, the oils like to co-distill with the solvent (naphtha). It seems as the solubility capacity of the solvent is pretty low. Centrifugal force
helps to a degree but time and alkaloids are lost in the added methods. Phase change separation also requires less solvent but again the time wasted.
My question:
Is there something that could be added to the aq to help push these oils from solution during the washes?
Boffis - 20-11-2015 at 07:05
When I extract purine type alkaloids I used dilute acid and then extract the aqueous leachate with an immiscible organic solvent to remove the fats
and waxes before I neutralise the acid and precipitate the alkaloids. These are then recrystallised from a suitable solvent.
I think this is basically what Ozone was discribing above.
[Edited on 20-11-2015 by Boffis]
Willsolvem - 20-11-2015 at 12:54
It is a repeat post yes, my question:
Is there something that could be added to the aq to help push these oils from solution during the washes?
I'm thinking that something could be added until saturation of the aq, maybe a salt or sugar?