(a) Simple sugars: Boil finely cut fresh leaves (or other plant part) in water for 5 minutes (96% ethanol or methanol can be also used). Filter or centrifuge. Concentrate the extract in the vacuum evaporator until ethanol is completely removed. The obtained aqueous extract can be analyzed directly by chromatography.
(b) From polysaccharides or other sugar derivatives: Analysis of the individual sugars of a polysaccharide or a plant glycoside can be made after hydrolysis. Hydrolysis is performed with 1 M H2SO4 or 2 M HCl:MeOH (1:1) in a boiling water bath for 30 minutes. Sugar analysis on the hydrolysates must be performed prior to removal of H2SO4. It may be removed as BaSO4 after addition of equimolar quantities of BaCO3 solution followed by centrifugation. In plant glycoside, the aglycone moiety can be removed by extraction with ethyl ether or ethyl acetate. Sometimes ion exchange resins (i.e. Amberlite mixed bed) are used to remove the acid under mild conditions. Then, the sample is ready for further analysis.
(c) Components collected from plant secretions (nectar and honey): Collect nectar from flowers with glass capillary tubes. Make different dilutions of nectar and honey by adding distilled water and analyze their composition by paper chromatography (PC).
3.2 Sugar Alcohols
Experiment 2: Extraction of Sugar Alcohols Principle
The same as for simple sugars.
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