I have leaf powder of some plants. I am done with almost all the solvents I needed using Soxhlet, now the only left one is aqueous extraction. Please help, whether to continue with soxhlet or not (Go for cold extraction).
In the caase of having performed the leaf powder extractions in a Soxhlet apparatus with non polar /CHCl3, THF.../ medium polarity /CH3COCH3/ and polar solvents ethanol,, methanol... etc./ you may continue with cold water extraction.
Whether to continue with extraction of the powder with water or not, it strongly depends on the contents of polar extractives in the sample and their solubility in the medium polar and polar solvents used before.
Water extraction can be performed in a glass flask at ambient temperature. Time of extraction 8 to 24 h, depending on dimmensions of leaf powder particles and possible stirring. The powder to water ratio should be high- 1:50 w/w and more.
In the sample, there may be a variety of polar compounds depending on their structure and origin /salts of organic and inorganic acids, monosaccharides, oligomeric saccharides, low molecular weight proteins, aminocarboxylic acids, phenolics, tannins, starch, lignols, dyes, vitamines.....
Note: in some cases also hot water, or even hot alkali water, extractions are to by performed. Usually in the case of extraction of bark from some conifers containing suberine and resinoidic acids. Hot water and alkali extractions, however lead to chemical alterations of the sample composition and properties.
Regards.
No.
It is not advisable to go with soxhlet in case of water as a solvent. Because the main principle of soxhlet is boiling point. If you are not dealing with thermolabile constituent, then only it is preferbale. But care must be taken to extract only thermostable constituten from particular plants.
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