More on Willow from the 2003 revised edition of Potter's Herbal Cyclopaedia:
"In the body, the glycosides are hydrolyzed to salicylic acid and this was until recently considered to be the active principle. However, it is now known that effective dose levels of Willow bark produce lower blood levels of salicylic acid than would be expected to be active, and the side effects on the gastrointestinal system experienced were much less than those with aspirin. This suggest an enhanced effect for the extract, rather than it being merely a source of salicylic acid, and confirms that the total extract is more efficacious than a single isolated substance."
This is one of the many benefits of whole plant medicine as opposed to standardized extracts.
Oh and I recently came across UK based the Herbarium.
From the site:
"The Herbarium is the creation of a small, autonomous group of independent herbalists. We have come together in a spirit of cooperation, to share knowledge and resources, and to explore a different way of organising ourselves in this rapidly changing world.
We do not consent to the erosion, by regulation, of our common law freedoms and rights. We therefore oppose the current attempts to turn traditional western herbalists into the poor cousins of doctors, using herbal ‘products’ as if they were the poor cousins of drugs. Our focus in these times of transition is to rehearse our skills in preparation for energy descent, climate change, and the collapse of unsustainable bureaucracies and power structures.
The Herbarium is intended to form a repository of information and to hold a safe space for a free exchange of ideas. Access is open to the public as well as our fellow herbalists. This is in keeping with the Culpeper tradition – whenever the living tradition of herbal medicine finds itself beleaguered, we share our knowledge with the people at large, so that they can claim it as their own, use it for themselves and keep it alive and relevant."
It looks like an excellent resource.