Chemistry - constituents of medicinal herbs

Alkaloids
This is a very mixed group of plant constituents that mostly contain a nitrogen bearing molecule (-NH2) that makes them particularly pharmacologically active. Examples are; Vincristine which is derived from the Madagscar Periwinkle (Vinca rosea) and is used to treat some types of cancer. Atropine found in Deadly Nightshade (Atropa belladonna), has a direct effect on the body, reducing spasms, relieving pain and drying up bodily secretions
Andrew Chevallier, Encyclopedia of Herbal Medicine, Dorling Kindersley, 2000
Anthraquinones
Anthraquinones are yellow brown pigments and many have been used historically as dyes for textiles, for example Dyers Madder (Rubia tinctorum). They are the main active constituents in herbs such as Senna (Cassia senna) and Chinese Rhubarb (Rheum palmatum), both of which are taken to relieve constipation. Anthraquinones have an irritant laxative effect on the large intestine, causing contractions of the intestinal walls. They also make the stool more liquid, easing bowel movements
Andrew Chevallier, Encyclopedia of Herbal Medicine, Dorling Kindersley, 2000
Bitters (Bitter Principle)
Used in reference to any of a group of unrelated constituents responsible for the bitter taste characteristic of many herbs. Bitters have certain physiological effects regardless of their chemical structure, since the bitterness itself directly stimulates tongue receptors, in turn sending signals via the gustatory nerve for the release of a cascade of gastric secretions and hormones. The effects are to stimulate appetite and digestive processes generally, increasing bile flow, regulating blood sugar levels and counteracting food sensitivities and allergies (Mills 1997). Bitters are regarded as cooling remedies, and hence are also useful for fevers and inflammation
A. Pengelly, The Constituents of Medicinal Plants, Allen & Unwin, 2004
Cardiac glycosides
Found in various medicinal plants, notably in Floxglove (Digitalis purpurea) and in Lily-of-the-Valley (Convallaria majalis). Cardiac glycosides such as digitoxin, and convallotoxin have a strong, direct action on the heart, supporting its strength and rate of contraction when it is failing. Cardiac glycosides are also significantly diuretic. They help to stimulate urine production, thus increasing the removal of fluid from the tissues and circulatory system
Andrew Chevallier, Encyclopedia of Herbal Medicine, Dorling Kindersley, 2000
Coumarins
Coumarins are lactones of hydroxycinnamic acids, with cyclic skeletons. Different kinds are found in many plant species and have widely divergent actions. The coumarins in Melilot (Melilotus officinalis) and Horse Chestnut (Aesculus hippocastanum) help to keep the blood thin, while furanocoumarins such as bergapten, found in Celery (Apium graveolens), stimulate the skin tanning, and khellin found in Visnaga (Ammi visnaga) is a powerful, smooth muscle relaxant
Andrew Chevallier, Encyclopedia of Herbal Medicine, Dorling Kindersley, 2000
Fixed Oils
Fixed oils are universally present in plants, particularly their seeds, varying only in their abundance and chemical composition. Apart from their nutritional value, these oils are widely used for specific therapeutic purposes, associated with cardiovascular, autoimmune and numerous other chronic diseases. Linseed (Linum usitatissimum) contains 35% fixed oils, making it valuable in maintaining a healthy heart and circulation, and in preventing chronic inflammatory diseases
A. Pengelly, The Constituents of Medicinal Plants, Allen & Unwin, 2004
Flavonoids
Found widely throughout the plant world, flavonoids are polyphenolic compounds that act as pigments, imparting colour, often yellow or white, to flowers and fruits. They have a wide range of actions and many medicinal uses. They are antioxidant and especially useful in maintaining a healthy circulation. Some flavonoids also have anti-inflammatory, anti-viral and liver-protective activity. Flavonoids such as hesperidin and rutin found in plants such as Buckwheat (Fagopyrum esculentum) and Lemon (Citrus limon), strengthen capillaries and prevent leakage into surrounding tissues
Andrew Chevallier, Encyclopedia of Herbal Medicine, Dorling Kindersley, 2000
Glucosilinates
Found exclusively in species of the mustard and cabbage family, glucosilinates have an irritant effect on the skin, causing inflammation and blistering. Applied as a poultice to painful or aching joints, they increase blood flow to the affected area, helping to remove the buildup of waste products. Once eaten, glucosilinates are broken down and produce a strong pungent taste. Radish (Raphanus sativus) and Watercress (Nasturtium officinale) are typical plants containing glucosilinate
Andrew Chevallier, Encyclopedia of Herbal Medicine, Dorling Kindersley, 2000
Glycosides
The glycosides represent a diverse group of seemingly unrelated compounds. The factor that unifies the group is that all glycosides have a sugar or sugar like molecule attached to the main molecule. Glycosides have a reputation for augmenting the immune function and aiding in detoxification, and are the 'tonics' of the herbal kingdom. Because the glycosides being such a large group, they have been further subdivided into cardiac glycosides, anthraquinone glycosides, saponins, cyanogenic glycosides, bioflavonoids and lactone glycosides
Dr. Eugene R. Zampieron & Ellen Kamhi, The Natural Medicine Chest, M. Evans and Company, 1999
Gums
Many plants (especially those growing in semi-arid conditions) produce gummy exudates when bark is damaged which serve to heal a wound. They may have acidic, basic or neutral characteristics. Gums (and mucilages) are invaluable aids in the management of irritable digestive disorders, especially when ulceration is a feature. They also act as laxative agents or anti-diarrhoeal agents. The soothing demulcent effects of gums (and mucilages) also benefit irritable states of the urinary and respiratory tract
A. Pengelly, The Constituents of Medicinal Plants, Allen & Unwin, 2004
Minerals
Like vegetable foods, many medicinal plants provide high levels of minerals. Plants, especially organically grown ones, draw minerals from the soil and convert them into a form that is more easily absorbed and used by the body. Whether plants are eaten as a vegetable, like cabbage (Brassica oleracea), or taken as medicine, like Kelp (Fucus vesiculosis), in many cases the mineral content is a key factor in the plant's therapeutic activity within the body. Dandelion leaf (Taraxacum officinale) is a potent diuretic, balanced by its high potassium content, while the high silica content of Horsetail (Equisetum arvensis) supports the repair of connective tissue, making it useful in arthritis
Andrew Chevallier, Encyclopedia of Herbal Medicine, Dorling Kindersley, 2000
Mucilages
Mucilages are long-chain polysaccharides that combine with water to form a slimy, semi-solid mass. They are not confined to specific plant parts by may occur in roots, leaves, bark and seeds. Their primary action is local, by direct contact with the surface of mucous membranes or skin. Here they produce a coating of slime that acts to soothe and protect exposed or irritated surfaces of the gastrointestinal tract, a demulcent action. When this effect occurs on the skin it is referred to as an emollient action. Mucilaginous herbs tend to be ideal for topical application for a wide variety of conditions ranging from bruises, swellings to irritable dermatological lesions. Mucilages (and gums) are invaluable aids in the management of irritable digestive disorders especially where ulceration is a feature
A. Pengelly, The Constituents of Medicinal Plants, Allen & Unwin, 2004
Phenols
This is a very varied group of plant constituents ranging from salicylic acid, a molecule similar to Aspirin, to complex sugar-containing phenolic glycosides. Phenols are often anti-inflammatory and antiseptic, and are thought to be produced by plants to protect against infection and feeding by insects. Phenolic acids, such as rosmarinic acid, are strongly antioxidant and anti-inflammatory, and can also have anti-viral properties
Andrew Chevallier, Encyclopedia of Herbal Medicine, Dorling Kindersley, 2000
Phytosterols
Phytosterols are minor but beneficial components of the human diet since they may inhibit growth or tumours and help in regulation of blood cholesterol
A. Pengelly, The Constituents of Medicinal Plants, Allen & Unwin, 2004
Polyphenols
Polyphenols are represented by Tannins, broken up into Hydrolysable tannins and condensed Tannins (or phlobotannins), Flavonoids and Anthocyanins and are described below
A. Pengelly, The Constituents of Medicinal Plants, Allen & Unwin, 2004
Polysaccharides
Found in all plants, polysaccharides are multiple units of sugar molecules linked together. From the herbal point of view, the most important polysaccharides are the 'sticky' mucilage and gums, which are commonly found in roots, bark, leaves, and seeds. Both mucilage and gums soak up large quantities of water, producing a sticky, jelly like mass that can be used to soothe and protect irritated tissues, for example, dry irritated skin and sore or inflamed mucous membranes in the gut. Some polysaccharides also stimulate the immune system for example acemannan, which is found in the leaves of Aloe vera
Andrew Chevallier, Encyclopedia of Herbal Medicine, Dorling Kindersley, 2000
Proteins
These are members of a group of substances, which form the physical materials of tissues and fluids, such as muscles, blood cells, hair, nails, hormones etc. They are made of amino acids linked together in long chains of atoms. Protein is used to build and repair bones, teeth, organs, muscles, and to produce blood and other body fluids
T. Bartram, Encyclopedia of Herbal Medicine, Grace, 1995
Resins
These are hard brittle secretions from certain plants that soften on heating. Resins are often linked with essential oils (oleo-resins), but they are not volatile. Depending on the plant, resins act by stimulating white blood cell activity near infected mucous surfaces. However, such activity is only possible in alcoholic tinctures of the relevant plant, as resins are insoluble in water. Major resin and oleo gum resin containing herbs and their effects on the body include; Myrrh (Commiphora mol-mol); antiseptic, antimicrobial, astringent and stimulant; Capsicum (Capsicum frutescens); analgesic, pain reliever; Ginger (Zingiber officinale); cholagogue hepatoprotective effects; Asafoetida (Ferula assafoetida); carminative, expectorant and hypotensive
Simon Y. Mills, The A-Z of Modern Herbalism, Thorson 1989
Salicylic acids
Salicyclic acid is a carboxylated phenol. Plants such as Willow bark and leaves (Salix alba) contain salicin, which changes to salicylic acid in the body. This is the form that counteracts pain, relieves inflammation, and deters heart-threatening blood clots. The synthesized form is nowadays known as Aspirin
Isabell Shiphard, How can I use herbs in my daily life?, David Stewart, 2003
Saponins
It is the main active constituents in many key medicinal plants. Saponins gained their name because, like soap, they make a lather when placed in water. There are two different forms, steroidal and triterpenoid. The chemical structure of steroidal saponins is similar to that of many of the bodys hormones, for example oestrogen and cortisol, and many plants containing them have a marked hormonal activity. Wild Yam (Dioscorea villosa) from which the contraceptive pill was first developed contains steroidal saponins. Triterpenoid saponins occur more commonly, for example in Licorice (Glycyrrhiza glabra) and Cowslip Root (Primula veris), but have less hormonal activity. They are often expectorant and aid absorption of nutrients
Andrew Chevallier, Encyclopedia of Herbal Medicine, Dorling Kindersley, 2000
Tannins
These are produced to a greater or lesser degree by all plants. They are polyphenolic compounds that contract and astringe tissues of the body by binding with and precipitating proteins. They also help to stop bleeding and to check infection. Herbs containing tannin are used to tighten up excessively relaxed tissues; as in varicose veins, to dry up excessive watery secretions; as in diarrhoea and to protect damaged tissue, such as skin problems resulting from eczema and burns. Oak bark (Quercus robur) and Black Catechu (Acacia catechu) are both high in tannins
Andrew Chevallier, Encyclopedia of Herbal Medicine, Dorling Kindersley, 2000
Vitamins
They are essential to life. Vitamins contribute to good health by regulating the metabolism and assisting the biochemical processes that release energy from digested food. Many medicinal plants contain useful levels of vitamins. Some are well known for their vitamin content, such as lemon (Citrus limon) has high levels of Vitamin C, and carrot (Daucus carota) is rich in beta-carotene. Sea Buckthorn (Hippophae rhamnoides) can be regarded as a vitamin and mineral supplement in its own right
Andrew Chevallier, Encyclopedia of Herbal Medicine, Dorling Kindersley, 2000
Volatile Oils (Essential oils)
Volatile oils, which are extracted from plants to produce essential oils, are some of the most important medicinally active plant constituents. They are complex mixtures often of 100 or more compounds, mostly made up of monoterpenes. The extracted essential oils have many uses. Tea Tree oil (Melaleuca alternifolia) is strongly antiseptic, whilst Sweet Gale oil (Myrica gale) is an effective insect repellant
Andrew Chevallier, Encyclopedia of Herbal Medicine, Dorling Kindersley, 2000