Re: How do you get magnesium out of chlorophyll?

It is actually quite easy to remove magnesium from chlorophyll. Magnesium 
(Mg2+) is a positively charged ion. When the pH is lowered (increase in 
hydrogen ion concentration or H+), the magnesium is displaced by hydrogen ion 
and chlorophyll is converted to pheophytin, which is olive green. Heating green 
leaves has the same effect because it denatures cell membranes and releases 
acids. 

There is also an enzyme, magnesium de-chelatase, which can remove the 
magnesium. 
  
Pheophytin treated with copper results in a bright green compound with a copper 
ion in the center instead of magnesium. The copper containing molecule is more 
stable than natural chlorophyll. It has been used as a food coloring, 
mouthwash, and internal deodorant.

Reference


Removing Magnesium from Chlorophyll