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                      Alkaloid Extraction Doc - by Osmium
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To isolate alkaloids from plants, the dried and powdered plant material is
extracted with pet ether (or hexane, colemans etc.) first. This removes fats,
oils, terpenes, waxes etc. This extract is discarded.

The material is now subjected to an alcohol extraction, eg with methanol or
ethanol. The extract is evaporated to leave the crude alkaloids mixture.

This extract is partitioned between an diluted aq. tartaric acid solution and
ethyl acetate. Other acids like citric acid can be used, and other solvents may
substitute here. The ethyl acetate layer contains neutral and weakly basic
alkaloids. Evaporate the solvent to isolate them.

The aq. layer is neutralised with NH3 or Na2CO3 and again extracted with ethyl
acetate. The organic layer now contains basic alkaloids, while the aq. layer
contains quarternary ammonium ions.

Many alkaloids can be isolated directly from the alkoholic extract by
chromatographic methods. This is a separation which works well for tropane
alkaloids (atropine, cocaine, scopolamine):

The alcohol extract is fractionated by column chromatography on SiO2, solvent
chloroform followed by chloroform with rising methanol content. This separates
lipids and terpenes from the crude alkaloid fraction. The alkaloid fraction is
again chromatographed (SiO2; CHCl3 : MeOH = 10:1) to isolate the pure alkaloids.

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