Generally we use many solvents for plant extraction. such as methanol, Ethanol, water, chloroform, n-hexen etc. which one is more potent?
Polar compounds are extracted with polar solvents, you need know the polarity of the solvents and the substances that yo want extract.
Non polar solvents extract non polar compounds
Water is the universal solvent and boiling water extracts almost all substances like an infusion
Methanol or ethanol are generally useful, able to extract polar and non-polar compounds. As mentioned by Jose above, other solvents work with different compounds of differing polarity.
Once the active compound(s) are known, or their polarity is known, the extraction solvent can be optimized for your scaled-up extractions.
It depends on what you want to do. If you want to pharmacologically test a traditionally used phytomedicine that is usually used as a water decoction (hot) or extraction (hot or cold), you should use water in the same manner as the traditional medicine is prepared. When testing this in an animal model, take care to apply it orally (as in human treatment).
If you want to identify and isolate secondary plant compounds you should use methanol (lower boiling point) or ethanol (somewhat higher boiling point), pure acetone or acetone/warer mixtures. This is for most of the polar and semipolar constituents. However, for lipophilic compounds you should use lipophilic solvents such as petrol or (bit mor polar) chloroform. for some of these solvents you should take care; acetone is highly fire sensitive and liver toxic; chloroform shows liver toxicity; thus take care for a well working hood. Don't use diethylether because of its high tendency for explosion.
Factors should be considered when selecting a solvent:
polarity;
boiling temperature - this should be low in order to facilitate removal of the solvent from the product;
reactivity - the solvent should not react chemically with the extract, nor should it readily decompose;
viscosity - must be low;
stability to heat, oxygen and light;
coast and safety
The organic solvents more frequently used are:
aliphatic hydrocarbons: propane, butane, hexane
alcohols: methanol, ethanol, 2-propanol
hydrocarbons with a carbonyl group: acetone, methyl acetate
halogen derivation: dichloromethane, dichloroethane, freons.
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