Introduction
Plant constituents, or "Active Ingredients" as referred to by the pharmaceutical industry, are elements that have a marked, definable physiological and possibly medical action upon the body. Although these ingredients are not of immediate interest to a herbal healing approach, as the focus is on the whole plant not just a specific constituent, it is sometimes useful to understand these ingredients if only to reinforce or provide traditional scientific basis that support the benefits and use of herbs.
Acids
Weak acids, usually in the form of salts or esters, are present in most plants. They are chemically differentiated by how many carboxyl (acid) groups are present in the molecule. An example is an ester of Valeric acid from Valerian, used as a sedative in orthodox medicine. Formic acid found in Nettles causes the sting but can also be used in a stimulating liniment. Acids containing more than 12 carbon atoms form the basis of polyunsaturated and saturated fats which play an important role in nutrition. Aromatic acids, such as benzoic acid, are composed of a benzene ring and a carboxyl group. They are medically important as inhalants for upper respiratory congestion and infections and are useful externally for infections and irritations.
Alcohols
A molecule that contains what is called a hydroxyl group or groups is called an alcohol. It is a very large class of compounds that includes many oils, waxesm and the more familiar ethanol and isopropyl alcohols. Most of the following groups described fall under the chemical classification of an alcohol, but their properties are due more to their molecular shape than to the fact that they contain a hydroxyl group.
Alkaloids
These are alkaline nitrogenous compounds that effect the central nervous system. Many are toxic and are often addictive. Some of the compounds included in this classification include caffeine, mescaline, nicotine, and strychnine.
Anthraquinones & Glycosides
Long known for their purgative and dyestuff properties, anthraquinones and other closely related chemicals are usually found in plants as glycosides, combined with a sugar. The direct action of these compounds on the gut may cause griping pains and these plants are usually used in conjunction with carminatives to relieve such symptoms. Plants with these constituents should never be used to treat constipation due to spastic colon -- the pain and discomfort would be severe. Examples include Senna and Yellow Dock.
"Bitter Principles"
Includes the chemical compounds iridoids and sequiterpenes, as well as many others that have a bitter taste. A wide range of general actions are attributed to the Bitter Principle, including stimulating the appetite, improving digestion, and liver detoxification, as well as some specific actions associated with a specific herb. For example, Valerian and Hops are relaxing nervines, White Horehound has pulmonary and expectorant actions, while Bog Bean and Devil's Claw are anti-inflammatory.
Carbohydrates
Carbohydrates are the basic units of nutrition. Included in this class are the monosaccharides, polysaccharides (important in nutrition), pectins (complex polysaccharides that can be internally healing to the digestive system and externally used for ulcers and deep wounds), and gums and mucilages (well known to reduce irritation both internally and externally).
Cardioactive Glycosides
Cardioactive Glycosides are specific steroidal saponins that have a marked effect on the heart. Foxglove and Lily of the Valley are two plants often associated with these compounds, but they are quite common throughout nature. Other examples include Figwort and Mediterranean Squill.
Coumarin & Glycosides
Used in the perfume industry for their "newly mown hay" aroma, coumarins have not been well studied. Recent research shows that they play a role as anti-clotting agents and are the basis of the anti-coagulant drug warfarin. Anti-bacterial action of Coumarin is the basis of the use of Mouse-eared Hawkweed. Umbelliferone is another example, found widely in the Umbelliferae family as well as Aesuetin in Rupturewort and Lavender.
Cyanogenic Glycosides
A group of potentially lethal glycosides that release prussic acid on hydrolysis. Some plants such as Wild Cherry Bark, Almond, and Elder contain trace amounts of these compounds and are medicinally important.
Flavones & Flavonoid Glycosides
It is believed that approximately 50% of flowering plants contain this group of phenolic compounds in their leaves. Originating from the Latin word flavus for their usual yellow colour. These compounds have anti-spasmodic, diuretic, and heart and cardiac stimulant properties. Previously known as P1, the bioflavanoids are probably the best known members of this class. Naturally occurring vitamin C is never found without boiflavonoids. Rutin, found in Buckwheat, is another example of this class and can be used to strengthen capillaries and reduce easy-bruising tendencies.
Phenols / Phenolic Glycosides
These chemical structures are classified by the presence of a benzene ring combined with an alcohol. Most members of this class of compounds have antiseptic activity and are also anthelminitic and caustic. In order for the body to absorb this compound, they are usually naturally combined with a sugar to form a glycoside.
A familiar example of this compound is Salicylic acid, which is found free or as methyl salicilyte in many plants such as Meadowsweet and Willow. This is the basis of aspirin and a whole class of non-steriodal anti-inflammatory drugs (NSAIDs). It is here that may best show how the chemical may have a whole range of properties that are not necessarily those of the plant. Salycilates are well known to cause severe stomach irritation, even leading to stomach hemorrhage. However, in a plant such as Meadowsweet, the whole remedy can actually stop bleeding in the stomach. It is thus important to realize that the actions of a whole plant cannot always be predicted by knowledge of their constituents.
Other actions related to this class of compounds include fever reduction, general anti-inflammatory effect, increased volume and concentration of bile, and rubefacient actions when used externally. It is now known that this anti-inflammatory effect is due to an anti-prostaglandin and bradykinin action, which would also explain the use of salicylates as anti-blood-clotting agents. In summary, these are generally useful compounds that are quite safe when used in their natural plant context. Two other familiar examples are Eugenol from Cloves, which helps tooth aches, and Thymol from Thyme and other aromatic remedies which is a useful anti-septic and anti-fungal oil.
Saponins
This name is derived from the Latin sapo meaning soap, due to the properties of these compounds to froth or lather up when in water solutions. Saponins are one of the most important class of plant chemicals for the pharmaceutical industry as it includes precursors of sex hormones, steroids, and heart drugs.
This is an extremely complex group of chemical compounds that have been divided into steroidal and tri-terpenoid saponins by the pharmacologists, depending on their structural differences. Beth Root, Wild Yam, and Yucca contain saponins of the steroidal group, as they appear to act as precursors of female sex hormones, explaining their usefulness in menopausal complaints. Glycyrrhic acid and glycrrhizin found in Licorice is a good example of a tri-terpenoid saponins, as these express a strengthening effect on the adrenal gland and mimic the activity of adrenocorticotrophic hormone (ACTH), which is often implicated in many stress-related complaints. Other examples include Blood Root, Figwort, and Primrose.
Tannins
Tannins is a term generally applied to any chemical compound having an astringent property and there is a wide range of complex chemicals that fall under this description. The name originates from the use of tannins in the Tanning Industry for their precipitating and curdling action on protein molecules, resulting in the hardening of the animal skin. This same process is useful in wound healing and for conditions of the digestive system where tannins are able to reduce inflammation and inhibit diarrhea. NOTE: Long-term use of tannins will eventually inhibit proper absorption.
Volatile Oils
Well known and recognized for their aromas, volatile oils are not only sensory gifts but also valuable medicines. These complex, fascinating compounds require detailed explanation and are beyond the scope of this website.
Chemically, volatile oils are generally a mixture of oxygenated hydrocarbons and their polymers, and alcohols. Some of the components of volatile oils are: monoterpenes, pinene, geraniol, borneol, cineol, limonene, and thujone, to mention only a few. A volatile oil from a specific plant is a blend of a whole range of these components in different proportions.
Some of the properties associated with Volatile oils include antiseptic, antibacterial, anti-fungal, insect repellent, anti-spasmodic, anti-inflammatory, rubefacient et cetera.
Additional Info.
See Herbs - Introduction, for additional general herbal information.
