I just wanted to add that if you're making distinctions between the natural and the un-natural, unless you're talking about ghosts and related new agey crap, you're not thinking through your position.
Ever since we discovered fire, we've been doing funny things with our food. To concoct is human. To be human is natural. Pollan writes a lot of about this sort of stuff: Even when you think you're outside of nature because you're commanding an army of pepper plants in your backyard/farm, you should stop and think who's using who. Are you planting you growing your peppers or are you a vector to the survival of the capsicum genus?
It is natural to take NyQuil when you want to sleep. Back before we invented that, we had chamomile tea. Before that? Ferment something and enjoy the alcohol. Don't wanna sleep? Red bull? We've been drinking coffee for ages. Hell, if you want to go to the more obvious way, back in the 1800's an apple was considered the sweetest of things, able to induce a sugar high upon the person who ate it; now we're a bit desensitized, but it is still natural to seek that sugar/pepper/coffee/whatever high.
Ever since the dawn of man, we've been reshaping the stuff we find around us for our own benefit. It is natural.
Extracts? just another way to amp up whatever sort of stimulation we're seeking.