extraction from plant extracts

loki · guinea pig

swil recently discovered a source of sida cordifolia extract which is described as 'standardised 6% extract' and he was considering methods to purify this to 99% alkaloids (the main alkaloid, at about 0.8 to 1.2% of whole aerial parts is ephedrine, with small amounts of pseudoephedrine, PPA, vacicine, vascinone and vasicinol)

swil did some reading about the methods of steam distilling ephedrine and learned some good useful information. ephedrine does not easily steam distill, and heating on the flask as well as external steam source is required to effectively do the job. The idea is to get the alkaloids out of the extract, not too concerned with the fact that other things like essential oils will come across with it, just with getting it out and away from the evil plant extract matrix. The evil plant matrix most likely contains hydrolysable tannins and sugars, which will caramelise and turn ugly in the process, will this impede the extraction?

One thing which is a concern is something swil had not thought of before, that ephedrine can form alkoxides with sodium and potassium hydroxides, so a different base might be helpful here. since the pKa of ephedrine is 9.6, magnesium or calcium hydroxide might be good, and these alkali do not have the capacity to form alkoxides due to their top pH capacity, 10 for Mg(OH)2 and 12 for Ca(OH)2. Is there any reason to suspect that this will not work? If these bases are good, they would be excellent choices for post reaction steam distillation as well.

After that step, presumably would follow extraction into a nonpolar then extraction to the HCl salt, and recrystallise, or alternatively, acidify, defat, basify, extract, dry, convert to HCl.

swil had thought of starting by boiling the matrix in a nonpolar and/or ketone but it occurred to him that the natural form of the ephedrine may come out in this process. swil has learned the hard way that there's things in sida which are absolutely horrible pains in the ass which get worse when heated. Probably not a good idea.

any ideas or experiences with doing such a thing would be greatly appreciated.

loki · guinea pig

Another idea that occurred to swil was to start with basing the extract with a small amount of water and calcium hydroxide, and boiling with toluene over top, with stirring, to extract into the base, filtering the toluene from the solids, then distilling the toluene back, and then running the steam with heat underneath as well to steam distill the oil across.

The idea here would be to minimise the amount of plant gak that one starts the forced steam distillation with. I am guessing that the ephedrine will not distill across with the toluene, otherwise surely this would be the way to do it... so therefore, distilling the toluene back should concentrate the freebase ephedrine in the boiler, with the other oils coming across with the toluene, and the forced steam distillation would then bring the ephedrine across.

Another advantage of this would be that because the ephedrine is already isolated in the nonpolar, there would be little risk of damage from the base when steam distilling. Even if sodium hydroxide was used rather than calcium hydroxide. because of the above mentioned alkoxide issue, i am inclined to think that calcium hydroxide would be far superior.

swil is a veteran of plant dmt extraction, and had no idea what a bitch ephedrine was to extract from plants until doing all this reading just today. gaaah. every little functional group adds speed bumps to the road. can't distill dmt with steam because it's unstable with the base, but overbasifying is only a problem from decomposing the dmt, not from changing it to a more polar chem again. o well, them's the breaks.

Enkephalin · Sat Jun 11, 2005 7:13 am

An aliquot of 200 mg of the ground ephedra plant material was weighed into a 15 mL centrifuge tube. Two mLs of aqueous 0.65 M KOH solution, 1.2 grams of NaCl, and 2.0 mL of diethyl ether were added to the tube, shaken for two minutes and centrifuged. The diethyl ether was collected and dried over sodium sulfate. Reported alkaloid recovery was 96.6-100.1%

From rhodium.
Would that not work?

loki · guinea pig

it would indeed. it would also mean that the idea of taking the plant material and basifying with toluene on top would definitely work too. doing that and then distilling the toluene back and then forced steam distillation would probably get the 100% figure consistently.

I am very fond of the idea of using calcium hydroxide as the base for this because it can be used virtually dry. maybe Ca(OH)2 and ethanol, with toluene on top, then distill the ethanol out, which should send the freebase into the toluene, then separate the tolly and spent plant material and distill back the tolly and then forced steam distill