What are all the other alternative solvents to dimethylsulphoxide (DMSO) that can be used for plant extraction?
Give a list of them.
Dear Mac,
The use of a solvent for extraction depend on the target compounds. Solvents used for extraction are categorised as follows:
Most polar such as methanol, ethanol, acetone etc
Semi-polar such as ethyl acetate, chloroform etc
Less polar such as hexane and petroleum ether etc
Therefore it is good to know your target compounds to enables you to choose suitable solvent.
Regards
What do you want to look for? You probably do a very nice extraction of plant materials every day with hot water when you make tea. This is a great procedure for the isolation of caffeine or theophylline. If you wanted to look for waxes and very hydrophobic compounds, you could use hexane, cyclohexane or other small paraffin liquids. If you have ever seen a shot of ouzo poured into a glass of water and turn milky, you have seen that ethanol can extract anisole and other aromatics into solution and that they drop out of solution in the presence of water. While DMSO is a good solvent in that it dissolves many, many compounds, it is also a pain to work with since it is very hard to evaporate. I have used many different solvents. Here is what I would ask myself.
1. Am I looking for water-soluble compounds? If yes, use water. If the compounds I
2. If the compounds I want are water-soluble and have a nitrogen, I would use mildly acidic water. If the compounds I want are water soluble and acidic, I would use mildly alkaline water (maybe a little NH4OH in solution).
3. If the compounds I want are very hydrophobic, use a non-polar solvent like hexane, heptane, etc. Smaller alkanes are too flammable and larger alkanes are too hard to evaporate. You can also use benzene, toluene or xylene but most people try to stay away from exposure especially to benzene.
4. If the compounds I want are polar but only slightly water soluble, I would use ethanol, methanol, isopropanol, acetone or acetonitrile. But all of these are flammable. On the other hand, they are all easy to evaporate from the solution. I have used ice-cold acetone many times to isolate plant products.
Use the cheapest, cleanest, least toxic and most volatile solvent that will extract your sample from the plant. A favorite is supercritical carbon dioxide (same polarity as benzene). It extracts well and turns into gas to give the dry extract. Unfortunately, you need special equipment for supercritical extractions.
A solvent used to make an extract should be easily removed. DMSO is very hard to remove and cannot be used.
It depends on what you want to extract from the plant materials and also on the nature of plant materials, as already said Dr Olechno and Dr Yunusa. Ethyl acetate may solubilize low and medium polarity compounds. If you are seaching for this kind of compounds ethyl acetate may work well. Otherwise, if you don't know the possible constituent of plant materials the best choice is to use a wide solubility solvent as ethanol, or perform a sequential extraction with solvents at different polarity starting the extraction with the less polar i.e. hexane or pethroleum ether and then use more polar solvents on the base of the elutropic serie. Common used solvents are also dichloromethane, acetone, diethylether, ethyl acetate, ethanol, methanol, water.
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