Chemical Constituents of Comfrey

Thomas J. Elpel, author of “Botany in a Day”, claims that it may be helpful to know what is happening at a molecular level in a plant to better understand how that plant may be used medicinally. However, “for the purposes of traditional herbalism there is rarely a need to know all the individual constituents of the plants. Herbalism is rooted in the basic properties, such as ‘astringent’, ‘mucilaginous’ or ‘aromatic’.” He advises against trying to dissect plants chemically as it may confuse, rather than teach. Additionally, “each of the individual substances may have different uses on its own than when combined with the whole of the plant. It is the overall pattern of constituents within the plant that is important.”

With the above information in mind, the chemical constituents found in the comfrey plant will now be discussed with the idea that although these chemicals exist, and can be studied separately, when they are combined with each other, the results may vary.

“The chief healing element in comfrey is allantoin, a cell proliferant which promotes the granulation and formation of epithelial cells.” A more simplified explanation is that allantoin “has the property of multiplying healthy cells and not malignant ones.” Comfrey contains from 0.6 to 0.8 per cent allantoin.

“The allantoin content of comfrey, especially in the root, has resulted in its use in folk medicine for healing wounds, sores, burns, swollen tissue, and broken bones. Allantoin, found in milk of nursing mothers and the fetal allantois, appeared to affect the rate of cell multiplication. Wounds and burns seemed to heal faster when allantoin was applied due to a possible increase in number of white blood cells. Comfrey has been reported to promote healthy skin with its mucilage content that moisturizes and soothes, while the allantoin promotes cell proliferation.”

Mucilage is also a very important chemical constituent in comfrey, and is found in even more abundance than in marshmallow root. “Mucilage is a slimy, moist polysaccharide…that moistens tissues. It is especially useful for mild burns and sunburns.” “The fluid between your body cells is a muco-polysaccharide hydrogel. The polysaccharides help strengthen this hydrogel after damage. It is typically described as an emollient when it is used externally on irritated skin, and as a demulcent when used internally, as for soothing a sore throat.” The mucilage in the comfrey plant occurs mainly in the root.

Comfrey also contains a fair amount of tannins. Tannins are substances that bind up proteins, which while doing so, gives them astringent properties. “An astringent is an acid substance that causes tissues to constrict. The most common natural astringent is tannic acid.” “Many plants that have astringent properties are also diuretic in nature…” (which) “…may be due in part to the tannins drawing water out of the cells, but also to the simple phenol glycosides that are often found with tannic acid. Since acids are generally harmful to bacteria, astringent plants are often also listed as being antiseptic or antibiotic.”

Other biochemical constituents of comfrey are starch, inulin, traces of oil, steroidal saponins, and pyrrolizidine alkaloids.

Energy is stored in a plant’s roots in the form of starchy carbohydrates. Elpel states that “Most starchy roots and seeds are edible, but some contain dangerous alkaloids or acrid substances.” In the case of comfrey, the root, then, must be the storage receptacle for the pyrrolizidine alkaloids that were mentioned in the above paragraph. However, these alkaloids are only considered dangerous if ingested, so that if they are used medicinally as drawing poultices to absorb toxins or to draw down an inflammation, the root might reasonably be labeled “safe” in this case.

“The word ‘Inulin’ is often confused with ‘insulin.’ Inulin is a non-digestible carbohydrate that can be converted to fructose through extended exposure to heat and moisture,…Plants that contain inulin (usually in the roots) are good for diabetics, since they are able to eat fructose.”

Steroidal saponins cause comfrey to be anti-inflammatory and to have pain-relieving properties. Saponins are often used medicinally to stimulate digestion; therefore they are often used in certain cases of arthritis where the pain is combined with indigestion or headaches. Saponins are also often used as diuretics.

Nitrogen that a plant does not utilize for protein production circulates in the sap or accumulates in parts of that plant in the form of alkaloids. “There are approximately 5,000 known alkaloids.” If a plant tastes bitter, it’s most likely due to the presence of alkaloids. Some alkaloids stimulate digestion, but many alkaloids also affect the nervous system in a powerful manner. They rarely affect the heart directly, but the central nervous system may be depressed or excited, as evidenced by circulation, respiration or blood pressure. Pyrrolizidine alkaloids, as found in comfrey, can be toxic to people and to livestock. The safety of pyrrolizidine alkaloids is controversial and will be discussed when contra-indications are addressed later in this paper. The highest concentration of pyrrolizidine alkaloids in comfrey occurs in the root of the plant, with a lesser amount occurring in the leaf.