Re: when I extract proline form plant tissue I dont know why most of the red c

Hi Shatha,

Thanks for your question. Perhaps a refresher on plant pigments would be useful. It should be noted that plant pigments are photon excitable dyes that are capable of transferring the energy of excited electrons… these properties are very important in photosynthesis and in dye mediated commercial solar energy production. However, for this discussion, we will address these photon excitable dyes as plant pigments.

There are basically three pigment groups that are present in plants. Within those three groups, there are many different types of those colors. The principal groups are Chlorophylls(green), Carotenes(yellow) and Anthocyanins(red).

Chlorophylls are a lipophyllic green pigments that are not water soluble. Chlorophyll absorbs red and blue light from sunlight energy and traps that energy. Therefore, the light reflected by the leaves appears green. Chlorophylls are contained in the membranes of chloroplasts, the site of photosynthesis.

Carotenes are also lipophyllic, they absorb blue-green and blue light. The light reflected from carotene appears yellow. Carotenes function as accessory absorbers to chlorophyll. The energy of the light absorbed by carotene is transferred to chlorophyll, which uses the energy in photosynthesis.

Anthocyanins are hydrophyllic, they absorb blue, blue-green, and green light. Therefore, the light reflected by leaves containing anthocyanins appears red. Unlike chlorophyll and carotene, anthocyanins are not attached to cell membranes, but are dissolved in cytosol or vacuoles. Anthocyanins are sensitive to the pH of aqueous solutions. In acids, the pigments impart a bright red color. If less acidic, its color is more purple.

The red color in your aqueous phase are anthocyanins. The exact chemistry of the anthocyanins would need to be investigated by chromatography.

We approximated your experiment given the few details: The anthocyanins in the acidic aqueous phase were bright red in color, as expected. The pink you noted in the toluene phase is due to the partial solubility of aqueous salicylate in toluene. This would also be expected and is what we have confirmed in our laboratory.

Thanks for your interesting question!
Peter

http://www.camse.org/scienceonthemove/documents/DSSC_manual.pdf
http://scifun.chem.wisc.edu/CHEMWEEK/fallcolr/fallcolr.html
http://www.chemie.uni-regensburg.de/Organische_Chemie/Didaktik/Keusch/D-TLC-e.htm
http://www.chemie.uni- regensburg.de/Organische_Chemie/Didaktik/Keusch/D-TLC_lipophilic_dyes-e.htm