Anthraquinone Dye

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  Dr R.T.Jadhav

  babie_mo_ko16

  We are having this undergraduate research about effective extraction of natural anthraquinone dye from a Noni tree bark. We tried using the traditional leaching process for starters using solvents like methanol and acetone. We started doing some experiments. We dried the tree bark and milled it. We leached the powder for a few hours (say 3). Then we did a simple distillation process to purify and extract the dissolved dye.
  
  The problem is that after leaching for 3 hours, the solution is still the same. We expected that the milled bark would be dissolved once the solvent is placed and being leached. But it appears that it did not. We used a 1:4 ratio of bark:solvent, and the solvent is diluted having it 50% solvent and 50% water. The solution formed was viscous(something like mud). We are at loss because it was not we expected. We expected to form a solution in which the solvent would fully dissolve the milled bark.
  
  I think there is something wrong with our ratio, but then we do not have enough literature in this. I could use some help, especially those who have experience in this field... 😕

  The Methanol or Acetone has extracted the dye. The problem is it has dissolved other ingredients also from the Bark. Further problem is you are adding water (50%) during or after the extraction. Water is much more miscible in the acetone/methanol and consequently, the dissolved material in the solution seperates out and becomes like mud. The very fact that you are drying the bark before subjecting it to extraction clearly indicates that the process should be carried out in anhydrous conditions.
  
  You should, therefore, carry out the removal of the solvent by distillation on a steam/water bath. You may get a sticky product, which if you triturate several times with small quantities of Petroleum ether may yield a solid product. This of course, shall be a mixture of several compounds which you may then subject to separation by various techniques such as coloumn chromatography to get the pure dye.