The failure of herbal, folk medicines to produce drugs which have a demonstratable value as a medical treatment is widely known to those who are close to the research.  This research has been both extensive and thorough.  It proceeds by separating the various substances in a folk medicine and then testing the substances which could be promising individually on animals.  Promising means that its chemical structure resembles somewhat a known useful drug; namely, a substance known to be bioactive.  It is tested in a variety of ways designed to sort out its potential. 

One of the most fortuitous examples was of the use of ergot by midwives.  It eased the pain of labor.  Dr. Albert Hoffmann, a Swiss researcher for Sandoz Laboratory, ran a series of tests on the various bioactive substance found in ergot, a fungus mold found on grains.  This was in 1938, when research was more of an art then a science.  In 1943, during a break between projects, he decided to test again one of the extracts of ergot, for it had some action in animals.  While making the 25^th derivative of ergot, one where he added diethyl amide to lysergic acid, he accidentally ingested/inhaled a minute amount of the substance.  He felt some strange effect upon his mental processes.  Having on prior days tested this derivative in animals, he decided to bioassay an amount of the substance well below the level known to be psychoactive.  To his surprise and the benefit of the world, he became quite high.  In his book "LSD, My Problem Solving Child" you will find his account of the experience and much more about this remarkable man. 

An aside note, ergot has been responsible for the death of millions. 

The mold which occurs on ripe rye and other grains contains a powerful vascular constrictor.  So powerful that gangrene has been frequently the result, most often of the hands and legs.  The farmers, not knowing of the poison, would not separate the tainted kernels, and thus the millers would unsuspectingly make flour. 

Sandoz Laboratory has marketed besides LSD-25, several drugs from the ergot extracts.  I suspect that these were no better than Ginko extract, for as we all know, drug companies are in it for the profit--though they would like you to believe otherwise.  Their researchers are more high-minded than the business men who run the companies. 

The mold appeared during wet harvest seasons and damp conditions of storing the grain.  This problem reminds me of another from Milk Weed.  The plant contains a heavy, fat-soluble alcohol.  For the cow that are lactating, most of the poison passes in its milk.  It is one of those poisons, like arsenic in small amounts, that accumulates in the body, and eventually produces illness and death.  It was not till around the 1920s that the mysterious illness was known to be caused by Milk Weed.  Abraham Lincolns mother died of it. 

{All this is from memory of things that I have read 20 years ago.}