How do medicinal herbs work?
One of the first questions that people ask when learning about herbal medicine is ‘How do medicinal herbs work?’ This blog post is an introduction to this fundamental question. For more detail on other aspects of herbal medicine, watch out for future posts.
White Willow (Salix alba)
Understanding the Healing Power of Plants
Plants contain organic compounds known as secondary metabolites. These are a natural product of the plant’s metabolism. They are not essential for the plant’s survival, like the primary metabolites, but the plant would suffer without them. This is because they are used for defence purposes such as to deter grazing animals or disease carrying organisms.
Medicinal herbs are plants containing secondary metabolites that have a therapeutic effect on humans or other animals. The study of the actions that these organic compounds have on the body is called pharmacology; a term which also applies to the actions of man-made pharmaceutical drugs.
When learning the indications of how to use herbs, Medical Herbalists are trained in pharmacology. This knowledge enables a very in depth understanding of how the herbs work in relation to how the body’s physiology changes during disease processes.
Examples of Pharmacology in Herbs
Bottle of aspirin, 1899 from Bayer Archives
Salicylic acid was isolated from Meadowsweet (Filipendula ulmaria) and White Willow bark (Salix alba) in 1838, then synthesised into acetylsalicylic acid in 1899 and called Aspirin. Salicylates and salicin have anti-inflammatory and analgesic (pain-relieving) actions and also bring down fevers. However, herbs containing salicin don’t cause gastric bleeding or ulceration in the same way that overuse of Aspirin can.
Meadowsweet’s Latin name is Filipendula ulmaria, but it used to be called Spiraea ulmaria after which Aspirin was named
In Meadowsweet, this is because it contains mucilage that has a demulcent action, which soothes and protects the stomach lining and has anti-inflammatory properties.
Other protective constituents in Meadowsweet are the tannins. These have an astringent action, so this means they create a barrier that protects the underlying tissue by binding with and precipitating proteins. In chemistry, precipitation means to create a solid from a solution. So, in a bottle of tincture that has a high tannin content, after a time and the contents settle, a dark coating may be seen around the bottom of the glass. In a similar way, a protective layer forms over the lining of the digestive tract.
The constituents of a herb are the active ingredients. These are the secondary metabolites that have a definable action on the physiology of the body and are used as medicine. It is better to use the leaves, roots, flowers, seeds, or bark etc. directly from the plant, rather than take out individual constituents to use in isolation.
From left to right: Chemical structure of salicylic acid, morphine and digoxin.
Pharmaceutical Medicine from Herbs
Opium Poppies (Papaver somniferum)
Photo by Wolfgang Horlacher
Most pharmaceutical drugs are derived from studying herbs and isolating constituents from them to create commonly used medicines. For example, morphine is isolated from Opium Poppies (Papaver somniferum) and digoxin from Foxgloves (Digitalis purpurea).
Just to be clear; I use these two examples (Opium Poppy and Foxglove) because most people will have heard of these common drugs, however they are both highly toxic plants and are absolutely not to be gathered or used by the general public. Meadowsweet and White Willow are fine to harvest yourself though. Always use a field guide to safely identify plants.
Foxglove (Digitalis purpurea)
Alternative Medicine?
So, that was a brief explanation of how herbs work. Every single plant used for medicine has its own profile of constituents. So, learning the pharmacology of the each one enables the Medical Herbalist to fully understand its indications for use. Herbal medicine was once the only medicine, and still is in many parts of the world. It has been used effectively for many thousands of years and the human race wouldn’t have got this far without it. The ancient wisdom from plants is now seeing a resurgence and I want to empower you with the confidence to make your own informed choices in healthcare.
Remember, the word alter-native means to change course from what is naturally occurring. Therefore, one could argue that Herbal Medicine is not alternative medicine after all, but the original, indigenous, native medicine of planet Earth!
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