In recent time the active constituents responsible for medicinal actions of plants have been studied and observed. The active plant constituents are usually classified by their chemical structure rather than actions. This list is not conclusive and just provides a basic overview of the main constituents including Alkaloids, Amino Acids, Anthraquinones, Coumarins, Flavonoids, Glycosides, Minerals, Mucilage, Saponins, Tannins, Vitamins and Volatile oils for a better understanding of medicinal plants.
Many herbalists believe that plant medicines are the sum of their constituents and cannot be reduced just to specific compounds, almost like reducing the entire visible colour spectrum to three primary colours, or a human being to a few atoms.
Alkaloids is a group of naturally occurring plant constituents, chemical compounds, that contain nitrogen atoms and is produced by a large variety of organisms. Alkaloid containing plants have been a part of our history for both therapeutic and recreational uses. Some well known examples include caffeine, nicotine and cocaine. They have a variety of purposes in plants, including storage and transport of acids, antioxidant protection and anti-predation effects.
A group of sugar ethers that are usually classified according to their chemical nature because they have vast medicinal applications and found in most therapeutic plants. Some categories of glycosides include alcohol (found in the genus Salix), coumarines as mentioned below, flavanoids, cyanogenic glycosides (used a sedative and relaxant), saponins (see further down), steviol and thioglycosides (various).
Cardio Glycosides are an organic compound containing a sugar called glycoside that act on heart muscles. They include glycosides like digitoxin, digoxin, gitoxin. An example is Foxglove, where the leaves are used as a cardio stimulant in congestive heart failure (1).
Minerals such as Calcium (sesame seeds, celery), Copper (cocoa), Germanium (garlic), Iodine, Iron (all green herbs), Manganese, Phosphorus (watercress), Potassium (dandelion) and Zinc (pumpkin seeds) are important in a healthy organism and preventing illness (1).
Tannins are produced in various amounts by all plants and the harsh taste makes them unpalatable to insects and animals. They draw tissues together (in varicose veins for example) and improve resistance to infections (1). They can also be used to dry up excessive watery secretions (diarrhea), protect damaged tissue (skin), help to stop bleeding (in heavy menstrual flow) etc. (3). There are some safety concerns with tannins. An example is Raspberry leaves and fruit which can reduce post-partum hemorrhage, heavy menses etc. (3).
Amino Acids are a group of a few hundred organic compounds that consist of carbon, hydrogen, oxygen, and nitrogen elements. They are called the basic building blocks of proteins. Their sequence determines the geometric structure of the protein they create, which amazingly determines the type and function of the protein they create. They play unique and interchangeable roles in plant and animal metabolism. An example is Tryptophan (5), called an essential amino acid because it iss essential for human life and cannot be synthesized by ourselves (needs to be included in diet from things like chocolate, yoghurt, eggs, sesame, some seeds, bananas etc.), is the precursor for serotonin, which for example can be converted to melatonin, these play a big role in mood.
Coumarins is a substance found in many plants with a variety of different actions, including blood thinning, anti-inflammatory, anti-hypertension, antiseptic, appetite suppressing etc. (various).
A good example is Celery, which is a sedative, anti-septic, anti-fungal, anti-inflammatory, analgesic, carminative, diuretic, uricosuric, anti-rheumatic, anti-gout, antispasmodic, stimulant, hypotensive, bitter, digestive tonic, galactagogue and a uterine stimulant. The coumarin Bergapten is found in celergy seeds (1).
Mucilage are found in many plants and are large sugar molecules that soak up water that produce jelly-like structures. They can protect against irritation, acidity and inflammation in the digestive tract (1). It is also said to absorb toxins and use for coughs and urinary spasms. Examples include Slippery Elm, Plantain, Fenugreek and Comfrey (1, 3).
Volatile oils are extracted from plants to produce various essential oils. In some plants it is the most important active constituent. According to Dr. Marciano they are a complex mixtures of many compounds and vary widely chemically (3). Volatile oils are usually combined with a carrier oil like olive oil or diluted in some other way with water or in foods. Some examples include lemon balm, ginger, peppermint, chamomile, ginger, eucalyptus and garlic.
Anthraquinones are active constituents that have an irritant or stimulating effect on the large intestine and are usually used to relieve constipation (1). An example is Aloe-emodin, found in aloe latex (3).
Flavonoids are distinctive and found in many plants. They have a range of actions including anti-inflammatory, cancer, anti-bacterial and cardiovascular diseases such as maintaining healthy circulation. They are found in parsley, blueberries, black tea, marigold, chamomile, hops and citrus (1, 6, 3).
Marigold for example has many medicinal actions, including: anti-inflammatory, anti-spasmodic, vulnerary, demulcent, styptic, antiseptic, antiviral, antiprotozoal, anti-fungal, anti-bacterial, cholagogue, diaphoretic, lymphatic, phytoestrogenic (3).
Saponins are found in many different plants and is either a Steroid or Triterpene fat-soluble chemical base joined to a water-soluble sugar molecule. Their actions can include include alterative, diuretic, expectorant, anti-catarrhal, anti-inflammatory, antispasmodic, aphrodisiac, antioxidant, emmenagogue, cardiac stimulant, hormone modulating, hepatoprotective, and adrenal adaptogenic effects (3). Liquorice / licorice and Alfalfa are two examples.
While medicinal plants usually contain vitamins there are some plants that contain a notable amount of a specific vitamin. According to various sources vitamins are organic compounds that cannot be synthesized by humans in sufficient quantities and must be obtained from diet and according to Wikipedia they are classified by their biological or chemical activity.
According to the Encyclopaedia of Medicinal Plants some of the most notable plants that prevent illness through vitamins include: Vitamin A from carrots and apricots, pumpkin, spinach; Vitamin B from potatoes, bananas, green beans, asparagus, mushrooms, avocado, nuts; Vitamin C in parsley and lemon; Vitamin E from seed oils and nuts; Vitamin K from Alfalfa and other leafy green vegetables like spinach (1, various).