Nature: a drug pusher?

Some time ago, I was talking to a friend of mine. She stunned me when she affirmed that "drugs" are not the same as "natural" remedies. Drugs which she bought at the drugstore were "chemicals", while plants and flowers were gentler, kinder, almost harmless, medicines. I tried to explain.
But but but… I know, it is confusing! And I am a scientist!!!

While I do not advocate taking home remedies to cure life-threatening ailments, it would be unscientific not to recognize that many active ingredients used in several drugs available at the drugstore were originally found in plants or animals.

Darwin's grandfather, a physician, used to prescribe digitalis (foxglove) to his patients with heart disease. Digitalis is the principal natural source of the cardiac glycosides digoxin and digitoxin; foxglove therapeutic effects are known since at least the late 1700'.
Colchicine, penicillin, quinine, and digoxin are all very potent and effective drugs which were isolated from plants or moulds, sometimes by trial and error (most of them), sometimes by error (penicillin - this is the greatest example of accidental discovery - and Fleming's genius).
Anecdotal evidence was a very important drive in the discovery of such drugs before the scientific method took over and standardized drug discovery protocols. But we all know that when we are desperate enough, we would try anything to make the pain go away.

My favourite plant is the belladonna, also known as the deadly nightshade. Belladonna ("beautiful woman" in Italian) is named after the use that in the past women made of the plant (including, according to Wikipedia, Cleopatra, the queen of Egypt).
Having large, languid eyes was considered an attractive trait (maybe it still is; I am not keeping up with fashion lately); ladies used an extract of the plant to dilate their pupils, so that they could achieve that elusive look (not without side effects such as blindness, increased heart rate, and the like), and snatch general Antonius (in ancient times), or poor Mr. Darcy (more recently). Fast forward to our century, and the same compound found in belladonna (atropine) is used as a mydriatic by ophthalmologists; in other words, it is still used to dilate the pupils. From fashion to medicine, from ancient times to modern day!
The deadly nightshade, as the name implies, is... deadly, duh. Eating even a small amount of the plant can cause serious problems, and while it still has great potential medicinal properties, it has to be used very, very carefully, because, as in any other plant, the concentration of active ingredients is highly unpredictable. A nightshade leaf could kill a person, or just cause a little tummy ache.
Rumour has it that the nightshade was the queens' favourite poison.
Give me poison ivy instead, it feels less dangerous...

Another favourite of mine, and a lot less deadly, is salicylic acid. As the name impies, it was first isolated from the willow tree (genus salix). If I remember my plant physiology classes correctly, plants use these chemical compounds to communicate between different parts of the plant ("hey roots, are you doing OK today?" - "No, there is an ant infestation" kind of conversation), and also to fight the proliferation of parasites. You should not be surprised to know that the curative properties of the willow bark have been known for several centuries, and even animals know about it - at least, my plant physiology book reported this fun fact about animals eating willow bark. As with the example above, dosing salicin (precursor of salicylic acid) from the willow bark is a hit or miss endeavour. Too little, and nothing happens; too much, and you'll have a hole through your stomach (wild animals do not have lawyers to sue a willow tree for damages). Besides, a little chemical modification (the addition of a methyl group on the side of the molecule) increases its transport through the stomach lining and makes it easier on the stomach. So aspirin was born in 1897.

The greatest obstacle with herbs and plants is that it is extremely difficult to get the correct dose of the active ingredient. Plants produce different compounds according to environmental variables, so they are not very consistent; many of these chemicals are a response to parasites or viruses, so they are only produced when a plant is under stress. Plants, of course, do not only produce the chemical we need, but also a number of other chemicals, which may have side effects and can cause more trouble than they are worth. Many chemicals are not stable, and are quickly degraded by heat and long storage time.

So, yes, drugs are very often totally natural chemicals (we should all know by now that everything is a chemical). Of course, we can try to improve on what nature has provided, but I totally embrace the notion of sipping chamomile tea to relax at the end of a busy day.

For more serious occurrences, I'll err on the side of caution, and pay a trained pharmacist to prepare my drugs with exactly the right amount of active ingredients, and dispense them safely. I am not a risk taker: playing Russian roulette with such dangerous plants is not my type of game...