To elaborate on why it is meaningless whether a drug is formed inside a plant cell or a laboratory, it is useful to understand how chemical reactions work.
Briefly, stable combinations of atoms, which we call molecules, occupy sort of a low point of potential energy. The fancy word is minima, and you can think of the concept like this: imagine a heavy ball on one side of a hill. It is sitting there, happy to do nothing because it is at the lowest location in the immediate area. This corresponds to a stable chemical compound.
It happens though, that there may be another low spot on the other side of the hill. This corresponds to a different, also stable compound, that may be a rearrangement of the atoms in the first chemical or may involve atoms being lost or gained. We will refer to the first compound as the precursor, and the second as the product.
So how do you get the ball over the hill? Well, that's the issue at the beating heart of synthetic chemistry. In order for the ball to move over the hill, energy must be applied, and one method that can be used is to input that energy in the form of heat. You can conceptualize this as the work necessary to push the ball up to the top of the hill. Once you get over the highest point of the hill, the ball will roll down the second slope of its own accord. That hilltop is analogous to what chemists refer to as activation energy, the amount of energy necessary to get a reaction going.
So what does this have to do with 'natural' versus 'synthetic' chemicals?
It has to do with the methods used in the lab and in a plant/animal/fungus cell to synthesize something.
In a chem lab, we literally push the ball the whole damn way up the hill. We do this in any number of ways which I will not get into.
In a cell however, the environment is controlled so that homeostasis is retained. So the addition of certain potentially toxic compounds or solvents or the addition of many joules of heat is verboten. Instead, plants use enzymes. Enzymes are giant unwieldy complicated proteins that are all folded up into ridiculously complicated shapes. Somewhere in their structure they will have an active site, where the precursor can interact. And by interacting with the enzyme, the barrier of activation energy is reduced.
This is analogous to the enzyme being like 'naw, fuck tall, steep hills' and magically shrinking the entire hill. The highest point is now much lower than it was, although it still acts as a barrier in that it still needs some energy to get going, just less of it. This means that we don't need so much energy to push the ball up the hill, to rearrange or substitute or remove atoms to make the precursor into the product. And thus we don't need to put so much heat into the reaction to make it work, which would likely be energetically impossible or improbable for the organism the cell is a part of.
---
As you can see, these are two different methods, but they do the same thing: get the ball over the hump of the hill. In a lab with highly energetic methods of heating, we can pour energy into the reaction to our hearts' desires. But an animal or plant or fungus (or bacterium or archaea) with a certain budget for energy related to how much energy it's food contains this level of input isn't possible, so a way was found through evolution to shrink the hill so you don't need so much input.
Now for the caveats: this is an incredibly simplistic description. We chemists can also use methods other than best to improve the conditions for a reaction, like using bases to eliminate atoms via E1 or E2 mechanisms, and we can also use catalysts. Catalysis is what enzymes do, but we usually use inorganic stuff like aluminum or platinum instead of enzymes, for purposes like reductive animation or catalytic hydrogenation. Also the hill in real life isn't always smooth, usually there are transition states, which are like plateaus on the hill that correspond to states in between the precursor and the product.
But there is no caveat relating to what enzymes do in organisms or we do in the lab. It is literally the same thing. Two different methods no doubt, but the same starting and ending points. This is why you can make be same drug in a lab as in a cell. If there was something unique to either environment then you wouldn't be able to produce the product both ways, and we can in fact produce it both ways.
We make LSD like spiders make their silk.
