Friday, September 19, 2008

What's Chemistry Got to do With It?

When someone initially gets interested in herbalism they often have no idea that they will eventually need to understand the basic chemistry of herbs. But most of us will need to dive into this arena. For some it may be about understanding the science of herbs and for others it can be a necessary step to making potent plant medicine. 

For those people interested in the western bio-medicine approach to herbalism,  understanding plant constituents gives insights into how herbs work. For example, turmeric is high in curcumin which has been studied extensively and found to have a wide range of benefits or medicinal actions. Therefore turmeric is considered to be therapeutic because of it's plant constituents. (In contrast, or complement, to traditional herbalism which tends to look at herbal actions and energetics to determine use.) 

This article is focused on basic understandings of plant chemistry for the purpose of making potent plant medicines. Or why extracting poplar buds in 20% alcohol is not a great idea or why extracting marshmallow root with 95% alcohol probably won't work out well. 

The following is a very basic list of constituents and the mediums they are soluble in to help beginning herbalists making plant medicines. 

To delve into the chemistry behind plant constituents please refer to the reading list at the end of the article.

Common Chemical Compounds
Soluble: alcohol, water, vinegar
Alkaloids posess a huge variety of effects ranging from benign to extremely poisonous. They are extracted extremely well by alcohol and much less so by water (Cech). Plants high in alkaloids are goldenseal, lobelia, and motherwort. Alkaloids can be sometimes dissipated with heat or tannins, or magnified with vinegar (Cech).

Soluble in: water, alcohol
A glycoside is chemically described as a compound that contains a sugar as part of the molecule. There are several different types of glycosides with a variety of effects including beneficial and toxic effects on the heart (cardiac glycosides found in Digitalis and Hawthorn), laxatives (anthraquinone glycosides found in senna, rhubarb), and antiseptic qualities (arbutin found in Uva ursi). Stevia, rebaudiana bertoni, another glycoside, has 40-300 times the sweetness of sucrose.

SaponinsSoluble in: water, alcohol
Saponins are a special type of glycoside. We use saponins (hopefully) daily in our soaps. Saponins break up fat molecules (think of the Dawn commercials and the big piles of dirty dishes). They also have a variety of other effects including adaptogenic, diuretic, anti-spasmodic, and expectorant (Cech). Horse chestnut, licorice, and chickweed all have saponins.

Soluble in: water, alcohol
Flavonoids are another type of glycoside. Among the important effects of flavonoids is their antioxidant effect. An antioxidant is a molecule capable of slowing or preventing the oxidation of other molecules. They are also known to decrease capillary fragility.

Soluble: glycerin, water, alcohol
Oak, tea, witch hazel, and red clover all contain tannins. Herbs with high tannin content are generally used as an antiseptic, a styptic, and to shrink tissues. Tannins are rendered inactive with the presence of milk and may have the ability to render some alkaloids inactive (Kress, Cech).

Soluble: Water (Cold preferred)
Soothing to the gut and urinary system, herbs high in mucilage also tend to be nutritive and nourishing to the immune system (Cech). Herbs with high mucilage content include marshmallow, mullein, comfrey, and slippery elm.

Soluble: water
Generally immune stimulating and nutritive, herbs high in polysaccharides are burdock, astragalus, and boneset (Cech).

Minerals, trace elements
Soluble: water, vinegar

Soluble: water,
Vitamins A, D, E, and K are fat-soluble, with the rest being water soluble.

Soluble: alcohol, oil
Resins are typically expectorant and bitter. Herbs containing high amounts of resins include cottonwood buds, calendula, and gumweed.



Water extracts almost everything with the exception of resins. Different temperatures may effect the extraction (simmering for barks and roots, just boiled for leaves, cold for mucilaginous plants). Some herbalists prefer to use distilled water.

Marshmallow cold water infusion

Almost everything is extracted by alcohol with the exception of minerals and trace elements. The percentage of alcohol used in plant medicine can be determined by it's plant constituents. For example, resins must be extracted in 95% alcohol (cottonwood buds, propolis and myrrh are good examples). Other alcohol percentages for certain plants are based on scientific queries into constituents or personal preference. Richo Cech has a nice listing in his book, Making Plant Medicine. 

Mucilage is extracted by alcohol and then broken down by it, so it's best to use a cold water infusion and then add just enough alcohol if wanting to preserve it. 

Proof vs. percentage
In the above photo you can see it listed as 100 proof. The alcohol percentage is half of the proof. So in this case the above vodka is 50% alcohol. 

Everclear (which is only available in certain states) is 95% alcohol - the highest percentage possible. (Note that some states carry everclear at 151 proof only, be sure to check.) 

Many vodkas, brandy's and other liquors are 40% alcohol. In general it is best to choose a pure alcohol, not one that is flavored (with who knows what!). 

Glycerin is a sweet substance made from plant or animal sources and is chemically related to alcohol. It's made by the breaking down of fat and oils with the use of high pressure steam (Cech). Herbalists use glycerin to extract medicinal properties from plants when wanting to avoid alcohol. 

Glycerin does poorly at extracting properties with dried plant material so fresh plants are highly recommended. According to Henriette Kress, some minerals and trace elements, some alkaloids, some acids, and some mucilage are extractable with glycerite. Richo Cech reports that tannins are extracted very well by glycerin.

Glycerin being added to a willow bark tincture to further extract tannins. 

Oils have the ability to extract oils and resins.

Calendula flowers extracted into olive oil. 

Vinegar has the ability to extract minerals, trace elements, and alkaloids. Most herbalists use apple cider vinegar, balsalmic vinegar, or other high quality vinegars. (Distilled white vinegar is not reccomended for internal use.) 

Besides extracting a variety of constituents, vinegar can also add other benefits to the end product as well. It is considered specific for digestion and the respiratory system. 

Chickweed being extracted with vinegar. 

Further Reading

Making Plant Medicine, Richo Cech

Henriette Kress' website:

The best resource on herbal chemistry is Lisa Ganora's book: 

Herbal Constituents: Foundations of Phytochemistry

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