Interesting. Do you have any links to scientific publications regarding this subject? Or maybe some landmark papers? The concept is very interesting but I fail to see a suitable application for let's say, stem cell transplantation due to the very different composition of plant cells compared to human cells.
The human immune system would attack it immediately and probably efficiently too.

So that would leave an extraction process as you mentioned, however wouldn't this just be another excuse for pharmaceuticals and other companies to continue overcharging customers/patients for creams that hardly work and need to be applied forever to maintain their effect?
Having a renewable source implanted would solve this, but again, plant stem cell implantation in humans wouldn't work as I mentioned earlier.

Still, very interesting concept!