Here's an interesting article I ran across from Wired entitled "Amazing Chemicals Invented by Nature, Rebuilt in Lab".
Natural substances can treat cancer, prolong life and trigger amazing hallucinations.
But although nature can make a remarkably wide variety of chemicals — far more than the best molecule-making robots — it does not always deliver them in bulk. Drug companies and medical researchers often turn to organic chemists when they need something that is too rare or too difficult to harvest from the wild.
Click on the thumbnails at the bottom right of the article and you'll come across things like,
"The substance used to make the drug, shikimic acid, is found in Chinese star anise and was in short supply."
My favorite was on the Death Cap mushroom (not as cool a name as the "Destroying Angel A. virosa, but...), Amanita phalloides. "Eat a deathcap mushroom, and your next stop is the morgue. It contains a chemical called amantin, which destroys the liver and kidneys."
(Here's the interesting part) "But that's not all. It has another poison, called phalloidin, that sticks to the scaffolding of cells. That substance is less deadly and has a useful purpose: By attaching the toxin to a fluorescent dye, researchers can study the inner workings of cells, and watch how they divide. Those observations can shed some light on how cancer works and the way tissues grow."
So, check out the article.