What do you really mean by "in nature" and why do you think it's superior to whatever else it is that you've arbitrarily defined not to have the status "in nature"? It sure seems to me that the "nature" is used here as some sort of magical/mystical distinction rather than anything real and tangible.
Please. It's like you can't understand the difference between a runners high and a heroine injection.
The chemicals that humans were exposed to in significant concentrations were basically unchanged for a hundred thousand years or more. Those chemicals which have increased in concentration in our immediate environment since the advent of agriculture (or the industrial revolution, if you prefer) are hereby deemed non-natural chemicals for the purpose of this discussion.