aga
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Plant Material Extraction
Now i know this sounds like drug-related crap, and it is, although not illegal drugs nor anything to get you high.
Having spent about 9 days attempting to isolate a compound from a plant (my first try ever) several things have become apparent :-
1. The solvent used has a huge impact on all processes following the extraction.
Ethanol or water just gave unfilterable soups. Acetone/water is currently working the best, at least insofar as the subsequent filtering step.
2. Inevitebly there is fine particulate matter that rapidly clogs filter papers and sinters.
Without a centrifuge, can these be removed to any degree ?
3. All filtrates end up brown after a short time (24 hrs max).
Adding activated carbon and re-filtering clears the filtrate up a little, which will help if crystals ever form. No idea if the AC also removes the
target compund(s) as i have not isolated any yet, so cannot re-do and compare yeilds.
4. Can a solvent destroy the target compound(s) present in the vegetable matter ?
Using a jug and just shaking the mashed up vegetation with the solvent (3 days) produced much more brilliant green precipitates.
Soxhlet extraction (>30 cycles for just 200g of material ... 2 days) produced 'other' browner precipitates, presumably due to the heat.
If anyone has some experience with plant extractions, i'd love to hear about it.
So far, it appears very tricky indeed to grab a bag of carrotts (just for example) and wind up with a dish of white crystals.
Unfortunately i cannot say what i'm after at this time, as the overall project is not mine, and this plant extract was an idea i had that might get
the project to where it needs to be, and much quicker/safer than the current plan.
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Sulaiman
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In the SM library there is 'The Plant Alkaloids' and other interesting reading,
and this small document may help
Attachment: Isolation of alkaloids.pdf (3.6MB)
This file has been downloaded 834 times
I have only a tiny bit of experience,
all I've discovered is that solvent choices are critical,
e.g. lots of solvents pick up vast quantities of chlorophyl which is rarely the desired product.
Most importantly, it has been done before ... lots of research helps 
P.S. liquid butane is a useful solvent, squirted down into (in my case) a chromatography column packed with your vegetable matter.
obvious but I'll say it anyway ... one can of liquid butane lighter refil releases a cloud of explosive gas... outdoors in the wind only!
If not, 'steam distillation' comes to mind.
vacuum filtering with papers I often leave the filter cake undisturbed and filter the filtrate again - I believe it's the filter pores getting blocked
that helps - visibly clearer (ususally)
[Edited on 23-12-2016 by Sulaiman]
CAUTION : Hobby Chemist, not Professional or even Amateur
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aga
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Awesome Sulaiman. Thanks. Very useful document.
Research is really hard when one forgets to look in the right places 
Until now i was unaware that the target(s) is/are 'alkaloids'.
Unfortunately one of them will not dissolve in an acidic environment.
That's bad for the extraction, good for the isolation later - IF the extraction works.
Butane is reputed to work for THC from cannabis, so that might work, even though i'm not after THC.
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Sulaiman
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I just remembered the most obvious ... chromatography !
CAUTION : Hobby Chemist, not Professional or even Amateur
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aga
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It's hard to stuff a cabbage (for example) into a packed hempel column.
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Sulaiman
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I assume that the first requirement is detecting for the presence of X, have you got a test for it ?
then determining potential yield and bulk extraction methods,
so I imagine pulped cabbage (in this case) at the top of a column is actually a good starting point,
mainly to evaluate solvents.
I have a few TLC plates that DJF90 donated to me,
I have u.v. lamps but nothing to power or hold them yet so not started TLC yet,
but a quick dive into chromatography literature put me off the subject for now ... it's not easy.
[Edited on 23-12-2016 by Sulaiman]
CAUTION : Hobby Chemist, not Professional or even Amateur
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ficolas
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What are you trying to extract? There are lots of articles about extracting X compound from Y plant, I remember lots of papers lile that when I was
excited about extracting stuff from plants, that was when this thread happened http://www.sciencemadness.org/talk/viewthread.php?tid=66475&...
I ended up doing only capsacin tho...
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aga
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Unfortunately i feel that i cannot say, as the overall process would be given away, and it is not my overall project.
If this was entirely my project, i'd have stated exactly what the objective is, and why.
My part is a bit of a long-range Hope, as i have no idea what to do with the isolated compounds to reach the target molecule, just that i 'feel' that
it would be a better starting material.
Probably best that i read the paper i found for a good few days before trying again.
Maybe i missed a part that is absolutely vital.
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DDTea
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You mentioned particulate matter is clogging your frit. Are you using any celite/filter aid?
"In the end the proud scientist or philosopher who cannot be bothered to make his thought accessible has no choice but to retire to the heights in
which dwell the Great Misunderstood and the Great Ignored, there to rail in Olympic superiority at the folly of mankind." - Reginald Kapp.
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Dr.Bob
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I have seen large scale plant extraction looking for actives in untested exotic plants for anticancer activity. What I saw was that the plant was
first air dried, ground up well, and first extracted by soaking the material first in hexanes, then moving through a series of more and more polar
solvents. They simply poured off the solvent slowly and washed the residue with a second shot of the solvent to rinse it. No fancy filtrations in
many cases, just careful decanting. Then they would rotovap each fraction and screen the crude residue for biological activity, then if it did
something, they would chromatograph the remainder into fractions to test further.
What this does is to extract the non-polars, oils and grease first, then as you move to ethyl acetate, acetone, acetonitrile, ethanol, methanol, and
then water you remove the increasingly polar compounds. That way even though you might only want the acetone soluble compounds, you might not want
the hexane soluble stuff mixed with the acetone soluble material. So doing stages of extractions can take more effort, but it can provide cleaner
material from each extraction, which may help remove the stuff that turns brown, or dilutes the desired material.
But unless you have a novel exotic plant, someone somewhere has likely done this already (the university I was at did 10,000's of plants a year) and
maybe even published the results, so make sure that you have researched the plant well first, as someone has likely already done something similar to
that before. Even if your material is novel, there is likely already something similar to it being extracted already. The technique that works
will be heavily dependent on the chemical nature of the desired material.
And Celite is the solution, mix some well with the solvent plant mix and then pour that material on a bed of it in your Buchner filter. Can't help
much more without some idea of what you are trying to extract.
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Magpie
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Do you have to use extraction? If the target is water insoluble with a high boiling point then try steam distillation.
The single most important condition for a successful synthesis is good mixing - Nicodem
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aga
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These particular compounds have been researched a lot, however i've not found any useful freely available data, including
melting/boiling/decomposition points.
I'll say exactly what they are when i can.
Thanks for all the excellent info.
Removing 'other' stuff first sounds like a great idea.
I'd never even heard of Celite either ! So much to learn ...
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DJF90
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Aga, please find attached a couple of books that may help you in your endeavours.
Attachment: Isolierung und Charakterisierung von Naturstoffen.pdf (3MB)
This file has been downloaded 492 times
[Edited on 24-12-2016 by DJF90]
Attachment: Natural products isolation 2ed - Sarker, Latif & Gray.pdf (7.6MB)
This file has been downloaded 563 times
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aga
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Wow ! What fabulous books DFJ90 !
Thank you very much.
Looks like this process is vastly beyond anything i've done so far.
Will do a lot more reading and try again.
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DJF90
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Natural product isolation is an extreme exercise in separation and purification of components, especially considering the sheer quantity of
extractable material and the (usually) small proportion that is the desired compound.
Take for example Frankincense, whose distinctive odiferous components were only isolated and their structures elucidated late this year; the authors
started with a couple of kilograms of frankincense and obtained a milligram of olibanic acid (thats a factor of 106!).
Attachment: The (+)-cis- and (+)-trans-Olibanic acids - Key odorants of Frankincense.pdf (1.2MB)
This file has been downloaded 427 times
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Eddygp
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If you're opting for filtration method (i.e. you know precisely the polarity of the compound you need), then Celite is certainly beautifully useful -
the pad on top of a sintered funnel makes everything go perfectly smoothly with no problems compared to not using it. It's kind of the same awe you
feel the first time you rotavap 
Purification would most probably be done with column chromatography.
TLC will give you an idea for solvents needed and how many impurities you're dealing with.
What else... play with pH or, if it has a carboxylic acid, check whether anion/protonated aqueous/organic separations are possible. If you're running
into huge problems with separations, play with the FGs - if you form imines from ketones, you can get all sorts of different properties from the
starting amine to aid in separation.
Of course, if you choose to get going on all these purification steps, only choose reactions with yields>97% or so (imine formation and hydrolysis
tends to be high yield so it should be good).
there may be bugs in gfind
[ˌɛdidʒiˈpiː] IPA pronunciation for my Username |
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PHILOU Zrealone
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The green color that turns brown is most likely chlorophyle.
I had the same when extracting schredded Laurus nobilis leaves...with methanol, aceton or ether.
The ether holds its green color longer.
For the rest of course extracting you don't know precisely what is hard.
But if you know what you are looking for then you can play with a sequence of extraction-decantation...with different solvents or mix of solvents; or
play with pH or with specific reactants of given chemical goups to improve your extraction or isolation procedure.
Soxhlet extraction, flash chromatography, reverse phase chromatography, ampoule-bottle extraction, increasing polarity extraction, rotavaporation,
TLC...all that was used when I worked into a anti-cancer lab with as main target the isolation of natural molecules from exotic plants to identify
anti-cancer or anti-metastatic properties...then after isolation, synthesis and derivatisation to improve the properties and provide patents for
pharmaceutical groups.
Working on fresh material or on dried material may sometimes provide different results and sometimes result into the isolation of different
molecules...biochemical processes at work when drying, oxydation, fermentation, maturation, ...
[Edited on 25-12-2016 by PHILOU Zrealone]
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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