of treatment, particularly for addressing one or more chronic problems.
Whole Plant Medicines
To stand up to scrutiny in a modern scientific world, herbalists now have to provide evidence of the efficacy and safety of the therapeutic herbs they use and apply the tools of the scientific world, biochemistry and pharmacology, to their task. While herbalists advocate the use of whole plant medicines, their enquiry necessitates that, for study and evaluation purposes, ingredients are singled out and their actions are ascertained. Such research enables quality testing, identifies efficient extraction methods and provides pointers to potential side effects and herb-drug interactions. Once this is accomplished it does not, however, tell the whole story and the knowledge gained from such study needs still to be incorporated into a more overall view of the whole plant. It has long been held that a herb is more than the sum of its parts, and, despite investigations into what are seen as the active ingredients in a given plant, there are other “lesser” constituents that have an equally important role to play therapeutically. These play an essential role in determining how effective the primary healing agents will be by rendering the body more or less receptive to their powers. Some of these “synergistic” substances will make the active constituents more easily assimilated and readily available in the body, while others will buffer the action of other potent plant chemicals, thus preventing the risk of side effects. It is the natural combination of both types of substances that determines the healing power and safety of any herbal medicine.
Opium poppies in Tasmania, Australia; some 50% of the world's crop used in medicine is grown here.
Before the development of modern scientific methods for isolating active constituents, whole plant medicines were used. Then, as science progressed, many of these constituents were able to be synthesised in the laboratory, perhaps in the assumption that synthetic compounds were similar to those derived from the plant world and as such would be assimilated just as easily by the body, and herbs became more or less redundant. However, chemical analysis of medicinal plants has demonstrated that there is a similarity in the molecular structure of components of plants and the human body, which makes the foods we eat and the herbs we use as medicines easily assimilated. The isolation and synthesis of potent active ingredients can produce an array of side-effects. Plant-derived drugs such as morphine, digoxin, ephedrine and atropine clearly need to be used with great caution. Even aspirin carries its risks and after 1986 all children's aspirin based drugs were withdrawn from the market due to their implication in association with Reye's syndrome in children, which can cause damage to the kidneys and brain.
Vinca, or periwinkle, is now known to be the source of vincristine, the anti-tumour drug.
Constituents of Herbal Medicines
Through photosynthesis, plants manufacture carbohydrates and give off oxygen, and through this process they create metabolic pathways that provide building blocks for the production of a vast array of compounds.
In medicinal plants these include minerals, vitamins and trace elements, and a vast assortment of substances known to have specific therapeutic actions in the body. The more widely known of these are as follows:
Phenols
Phenols, sometimes called phenolic compounds, are a large class of secondary plant compounds. They are aromatic alcohols and the building blocks of many plant components, and generally have antiseptic, antibacterial and anthelmintic actions. The simplest of the class is the antimicrobial phenol (C6H5OH). Another simple phenolic compound is salicylic acid, which forms glycosides found in willow, cramp bark, and meadowsweet, and has antiseptic, painkiller and has anti-inflammatory properties. It forms the basis of aspirin.
Other compounds include hydroxycinnamic acids, including caffeic, ferulic and sinapic acids, which form the basis of phenolic esthers, coumarins, glycosides and lignans; also cynarin, the main constituent of globe artichoke, with its liver-protective and cholesterol-lowering actions, and curcumin, the main component from turmeric, which is famous as an anti-inflammatory agent and also for its ability to lower blood pressure and protect the liver (Pengelly, 2004).
Other phenolic compounds include stilbenes, which occur in grape skins and red wine, with antioxidant, anti-inflammatory, anti-clotting and anti-allergy actions, and quinones, including anthraquinones (see overleaf) and naphthaquinones. The latter have antimicrobial and anti-tumour properties, for example juglone in walnut bark, and lapachol in pau d'arco.
Coumarins
Coumarins occur widely in plants, including black cohosh, wild oats, angelica, and horse chestnut, and they are generally antimicrobial and antifungal. The evocative smell of hay is due to the presence of coumarins that are lactones of hydroxycinnamic acids. They generally occur as glycosides, for example aesculin from horse chestnut. Dicoumarol that is originally derived from sweet clover (Melilotus officinalis) is used a strong anti-clotting agent, in the form of Warfarin, in allopathic medicine.
Furanocoumarins include angelican and archangelican from angelica roots, which are antispasmodic. These need to be used cautiously as they can cause photosensitivity, increasing the effect of sunlight on the skin, but they can also be used therapeutically for vitiligo and psoriasis. (Pengelly, 2004).
Anthraquinones
Anthraquinones occur as glycosides, and have a yellow-brown colour that has often been used for producing commercial dyes. They are found in senna, aloes, yellow dock, and cascara, and they pass unaltered through the stomach and small intestine, to be converted to their active form by micro-organisms. 8–12 hours after ingestion, they stimulate peristalsis and inhibit water reabsorption in the large intestine, producing a laxative effect. Their peristaltic action can sometimes cause griping in the bowel, so they are best combined with herbs such as peppermint, ginger or fennel. They are contraindicated in spastic bowel problems and pregnancy, and should not be used over a long period of time as they can reduce the normal bowel reflexes and cause habituation.
Tannins
Tannins occur widely in nature, often as glycosides, and they represent the largest group of polyphenols. Tannins are the main therapeutic constituents in witch hazel, agrimony, raspberry leaf, and meadowsweet. Their main therapeutic action is astringent, brought about by their ability to bind albumin, a protein in the skin and mucous membranes, to form a tight, insoluble protective layer that is resistant to infection. On the skin and in, the delicate linings of the mouth, the respirary, digestive, urinary and reproductive systems, tannins can separate bacteria that threaten to invade from their source of nutrition.
Tannins occur either as hydrolysable or condensed tannins. Sxq hydrolysable tannins have the ability to protect the skin and mucosa from irritation and to reduce swelling and inflammation. They have a drying effect that is useful for curbing over-secretion of mucous, bleeding and diarrhoea. Herbs rich in tannins make useful mouthwashes for infected and bleeding gums, gargles for sore throats, eyewashes for inflamed or infected eyes, remedies for catarrh, inflammation of the GI tract, diarrhoea, and heavy menstrual bleeding, compresses to heal burns, abrasions and cuts, and lotions to bathe haemorrhoids and inflammatory skin conditions.
Condensed tannins include oligomeric procyanidins, which have become widely known for their antioxidant and cardiovascular properties. They are found in green and black tea, red wine and grape seeds. Grape seed extract has been demonstrated to have strong antioxidant activity, protecting against free radical damage and cardiovascular disease, and preventing
