Basic Plant Chemistry

 In order to appreciate how herbs affect our bodies we have to consider their chemical Constituents and the effects that they cause. Herbalists tend to use the whole plant and therefore they do not treat with isolated components which mean that there can be quite chemical reactions in the body caused by ingesting. For example Sage contains a poison but there are other active components in it with nullify the effect of the poison in the body if it is taken as a whole plant medicine. The American FDA did at one point consider banning Sage but they proved it was safe taken as a whole plant, something most people have known for hundreds of years!!!!

Chemistry is divided into organic and inorganic branches.

Organic chemistry is the larger branch, dealing with molecules that have carbon as their ‘backbone’ framework; or ‘skeleton’ as the chemists call it. Carbon is a prerequisite for life as all living organisms have carbon atoms in their skeleton, generally attached to various other atoms including hydrogen, oxygen, nitrogen, calcium, magnesium and sulphur. In general, the more atoms a molecule has, the heavier it is.

To elaborate and provide a working example, simple carbon based molecules used everyday include the range of extremely volatile hydro-carbon fuels such as methane, butane and propane (1,3 and 4 carbon atoms respectively), as well as octane fuel which has 8 atoms. The myriad aromatic and therefore volatile components in plant essential oils generally have 10 or 15 carbon atoms. The aromatic plants are well utilised in cookery and herbal medicines.

The science of Chemistry has its own systems for naming molecules; which once grasped, makes understanding this complex subject slightly easier.

For example, all sugars end in the suffix –ose as in glucose and fructose. All enzymes (protein-based metabolic catalysing co-factors made from amino-acids) end in the suffix –ase, as in the starch digesting saliva enzyme amylase. Acidic substances are given the suffix –ates, so wherever you see this molecule name ending you know you are dealing with an acid, as in salicylates (salicylic acid) folate (folic acid), pyruvate etc.

Plant cells are ingenious mini-chemical factories, creating and destroying molecules for immediate and continual use throughout the organism. Due to the magic of photosynthesis, where water is split through the power of light, and gaseous CO2 is absorbed through microscopic holes on the underneath of plant leaves, an enormous range of secondary products are formed.  (This term ‘secondary’ was coined because none of the secondary plant metabolites have any nutritive primary metabolic function compared to certain other elements including carbon, nitrogen, potassium, oxygen, and other well known compounds such as the carbohydrates which are the primary products of plant metabolism.)

Medicinal plant chemists have cataloged thousands of the substances made in plants, although this is but a drop in the ocean when looking at the bigger picture of the 250,000 plants that could be investigated should humans not render them extinct beforehand.  Through this ongoing work, substances are classified into different ‘families of molecules’. We will be discussing them in due course. They include: acids, flavonoids, terpenoids, alkaloids, phenolics, steroids, tannins, polysaccharides and proteins.


All have the same basic building blocks and many are synthesised from similar biosynthetic pathways. Simple plant acids are discussed first. Weak plant acids are found in all plants. They are most often carboxylic acids with a general formula ‘–r-COOH ‘(r = the rest of the molecule). There are four main groups:

Monobasic acids- including aliphatic (straight chain) acids

Containing up to 26 carbon atoms per molecule, these include formic acid, acetic acid and a range of saturated and unsaturated fatty acids as well as valeric acid from Hops and Valerian.

Polybasic acids.
Containing more than one carboxylic group, very widely found in plants. Noted for slight laxative action and include oxalic, succinic and fumaic acids.

Hydroxyl acids.
These include both a pair of –COOH (acid) groups together with an –OH group (alcohol), giving them properties of alcohols as well as acids. These include citric, malic and tartaric acids.

Aromatic acids.
These are cyclic acids mostly based on benzoic and cinnamic acids. These are found widely throughout nature, but particularly in resins and balsalms. Derivatives of benzoic acid include salicylic acid of which there is much discussion of throughout these pages and on our foraging courses. Other derivatives include the phenols and tannins.

The most significant plant acids with regards herbal remedies are as follows:

Un-saturated fatty acids.
It is now widely known that certain fatty acids are vital for life. This is why the term essential fatty acid is used. Our bodies require them to build and repair cell walls, cell membranes and C.N.S tissues. Inflammation and other chronic diseases have been documented in people exhibiting a deficiency of polyunsaturated acids (PUFA’s) in the blood. The essential fatty acids are universally found in plants. Notable examples include linolenic acid (found mainly in growing green tissues) and arachidonic acid (found mostly in seeds and other reproductive tissues).

Recently, a lot of interest has developed surrounding one of the fatty acids, G.L.A (gamma linolenic acid). This substance is found in high quantities in both the Evening primrose and Borage (a.k.a ‘Star-flower’). Both of these plant oils are prescribed for an array of inflammatory disorders as well as certain rheumatoid conditions, eczema, as well as successful use in treating pre-menstrual syndrome.

Oxalic acid

This common substance is widely found in the Dock family (Polygonaceae), which includes the rhubarbs (Rheum spp), docks and sorrel (Rumex spp) and is also found in the tea plant (Camelia sinensis), spinach (Beta vulgaris spp) and parsley (Petroselinum crispus) amongst others. It forms insoluble salts with metals such as calcium and is often found in this form. This substance can impart a distinctive lemony citrus taste to plant leaves. One potential problem from over-excessive consumption of oxalates is the formation of urinary stones, which are produced by precipitation of excessive oxalates in acid urine. Another is gout, whereby joints accumulate large amounts of these crystal deposits bringing regular, extreme discomfort to sufferers.

Citric acid

Found widely in fruit and berries especially the citrus fruits. It plays a key role in metabolism and gives its name to the citric acid / krebs cycle involved in the production of useful energy from carbohydrates. It is classed as an alkaline food source because it breaks down quickly in the body to form bicarbonates. It causes increased bile flow from the liver and is noted as a gentle osmotic (water attracting) laxative and diuretic.

They are built from basic units called sugars and can be classified as to the number of sugars they contain.

These are simple sugars such as fructose, glucose, galactose and wood sugars, xylose, ribose and arabinose. Apiose from celery (Apiens graveolens) is another example.

These are molecules containing two sugar units including sucrose (glucose and fructose) maltose (glucose x 2) and lactose from milk only (galactose and glucose). They are quickly broken down by the body to mono-saccharides, although several such as raffinose, are reputed to contribute to the undigested CHO residue we call ‘roughage’


These are multi-sugar units, often extremely large molecules. Included here are the amyloses that constitute glucose storage molecules such as starch and glycogen, cellulose and inulin (a fructose based store found in the Asteracea family of plants including Elecampagne (Inula helenium), Jerusalem artichoke (Helianthus tuberosum), and Dandelion (Taraxacum officinale). This group also includes molecules containing other components beside sugar units, most frequently glucuronic and galacturonic acids, hemi-celluloses, pectins, gums and mucilages.

Immuno-stimulating polysaccharides

According to recent scientific research, a number of water-soluble acidic branch chained polysaccharides with high molecular weight exhibit significant immuno-stimulating properties. Plants showing these actions include the three species of Echinacea commonly used by western herbal medicine; Echinacea purpurea, E. angustifolia and E. pallida

Gums and mucilages

These are very common plant constituents that can be argued as being central to herbal remedies. Gums and mucilage’s are traditionally distinguished by their physical properties, a gum being notably tacky; mucilage’s slimy. However, there are no real chemical distinction between the two groups and so are discussed together.

The medicinal actions of gums & mucilage’s are more physical than chemical. They are made from uronic acid and sugar derivatives and even if broken down on digestion have little pharmacological effect. Mostly these molecules are resistant to digestive juices and many survive to reach the bowel. Yet plants containing them such as Marshmallow (Althea officinalis), Comfrey (Symphytum officinale), Ribwort Plantain (Plantago lanceolota), Slippery elm bark (Ulmus fulva) and Coltsfoot (Tussilago farfara) all affect the digetive, respiratory and urinary systems.

This is partly due to the reactions produced when coming into contact with mucous membranes. Gums & mucilages produce a coating of slime, which soothes and protects any exposed surface. For this reason, plants containing mucilage’s are primarily used as wound remedies, soothing pain, irritation and itching, and as they dry, they often bind to any damaged tissue. Their action is classed as emollient or demulcent.

This demulcent action continues along the digestive tract lining, which helps to explain the use of mucilaginous remedies for Gastro-intestinal inflammations, ulcers, lesions, as well as for reducing irritant results of excessive stomach acid or digestive juice secretion. To this end, slippery elm is a popular, effective treatment for relieving effects of acid dyspepsia.

Mucilaginous remedies also prove to be an invaluable aid for the treatment of digestive disorders. This is due to the fact that they soothe irritation that can be behind a range of symptoms such as flatulence, colic, dyspepsia, spastic bowel, vomiting and diarrhoea as well as many cases of abdominal pain. A working principle can potentially be applied here. For we notice that the extent they soothe irritation can often reflect in a reduction of those symptoms.

Two other systems are treatable with mucilaginous remedies, the urinary and respiratory. Whilst no useful parts of the mucilage’s reach those parts of the body, treatment is due to the relationship between the origins of the digestive and these other systems. During the embryonic development of the body, the tissues of these systems have a common source due to the bronchial tree developing as an offshoot of the gut. Therefore agents that affect the lining and wall of the digestive tract will, by reflex action, influence the function of the bronchial and urinary ducts.

These are a large and important group of plant constituents based on the phenolic molecule. We will look at the different types, which include simple phenols plus glycosides, tannins, coumarins and glycosides, flavones and glycosides, anthraquinnones and glycosides.

Simple phenols
In general the phenols are known to be bactericidal, anti-septic, anthelmintic and anaesthetic. The anti-microbial effect is probably due to reported structural damage to cell walls and internal components of the microbes.

These make up a large group of polyphenols found widely in the plant world. Tannins are known to have been used for centuries in the treatment of wounds and burns. Their role in plants are continually  speculated upon. They have been used by man for millennia to tan animal hides. This practice is utilising their underlying properties of precipitating proteins into insoluble complexes, then combining with these complexes and eventually rendering them resistant to enzymatic degradation. Their ‘complex-forming’ abilities are helpful when treating septicaemia.

When applied to living tissues, this property is astringent. As acids, they impart a sour taste, with resultant puckering of the protein lining the mouth and tongue. There are two groups of tannins; Hydrolysable and condensed tannins.

Hydrolysable tannins
These tannins are derivatives of simple phenolic acids. In large quantities they are toxic to the liver, which is why plants that contain them in large amounts are unsuitable for use on wounds. They turn brown on exposure to air and are responsible for the brown colour of many plant tinctures.

Condensed tannins
Also known as non-hydrolysable tannins, these are related to flavonoid pigments. When heated in acid they tend to group together and polymerise, forming insoluble substances known as tannin reds. Often seen to form in tinctures and fluid-extracts of some plants when standing for long periods, especially when in light, their presence is indicative of high levels of condensed tannins. Plant tissues containing them will often have a red colour. The final breakdown product after heating is a substance called catechol. This shows little toxicity to the liver or other ill effects, so their use is to be favoured.

It is worth noting that all tannins share these properties:

  • Solubility in water and alcohol but not in organic solvents such as oils or hexane gas
  • The forming of precipitates with proteins, nitrogenous bases, polysaccharides, some alkaloids and some glycosides.

The actions of tannins can be compared to mucilage’s in as much as they work as astringents, although for tannins this is only at the point of contact with the gut wall. Tannins are also haemostatics, used externally to arrest haemorrhaging and subdue exposed inflammations. They are of great benefit in treating mucosal surfaces lining the orifices so that herbs containing tannins are often used as eyewashes, mouthwashes, snuff and as treatments for rectal problems.

Internally, tannins will prevent additional cellular secretions as the exposed cell walls of the lining membrane pucker or contract following contact. Because of the nature of the narrow boundary between the interior and exterior of the gut wall, anti-inflammatory effects are enhanced; therefore tannins can be specifically used for controlling symptoms of gastritis, enteritis and inflammatory bowel conditions.


By simply inhaling the aroma of freshly cut grass, the senses are experiencing coumarins emanating from plants. They are found throughout the plant kingdom and particularly in the foliage of the legume family (Fabacea). A fermentation product of coumarin (dicoumarol), occurring naturally in spoilt clover (Trifolium pratense), is a potent anti-coagulant, well known for being the basis of the rat poison ‘warfarin’.

These substances are also widely distributed in nature. They are intrinsically connected with the metabolism of vitamin C. Some plants such as the citrus fruits (Citrus spp), Buckwheat (Fagopyrum esculentum), together with all white and yellow flowers have significantly high levels of flavonoids.

There are four main groups of flavonoids:

1) Flavones
Including apigenin in Celery, luteolin in Horsetail (Equisetum arvense). Also included are the Isoflavones (isomers of flavones with steroidal properties) eg: genistein in clover, gorse and other legumes.

2) Flavonols
Among them are quercitol (glycoside = rutin) found in Buckwheat, Rue (Ruta graveolens) and more than half of all plants tested, as well as kaempferol, also found in more than 50% of plants tested.

3) Flavonones
Included here are eriodicytol and methyleriodicytol, which together make up ‘citrin’ of citrus fruits. The glycoside is hesperidin. Another well-researched flavonone is Liquiritigetol in Liquorice (Glycyrrhiza glabra).

4) Xanthones
Include gentisin in Gentian (Gentiana officinalis).

The array of Flavones found in plants have a number of important pharmacological properties. Many are diuretic; others are documented anti-spasmodic, anti-inflammatory, anti-septic and even anti-tumour, although the main action of the flavonoid group appears to be on the vascular system. This has become known as a result of research carried out on the so-called ‘bio-flavonoids’, also known as ‘Vitamin P’; especially hesperidin and rutin.

These molecules are known to decrease capillary fragility and permeability, as well as being effective in lowering blood pressure. Allopathic practitioners treating the capillary symptoms of hypertension, diabetes, arsenic poisoning and allergic conditions often use rutin. Buckwheat has high levels of flavones so is often used by herbalists for much the same problems.


Bioflavonoids and Vitamin C

During 1936, research by Albert von Szent-Gyorgyiin discovered that scurvy was only helped when ascorbic acid was given with bio-flavonoids. Ascorbic acid is present in fruits and vegetables only with a bio-flavonoid complex. It is supposed that significant concentrations of bio-flavonoids in plants will be particularly helpful in dealing with circulatory problems. They act as a regulating factor in the peripheral circulation as well as exhibiting anti-inflammatory and diuretic properties. One plant previously discussed in booklet 1 with such actions is Hawthorn.

Volatile oils

These are complex herbal constituents; providing one of nature’s most potent treatment aids, although seemingly hardly recognised as useful by conventional pharmacologists. Generally speaking, volatile oils are mixtures of hydrocarbons and other oxygenated compounds made from them. The most common and simple hydrocarbon in a volatile oil is the terpene, built up by successive accumulation of isoprene molecules (C5 H8).

With different variations of this building block, a wide range of substances can be synthesised in plants, starting from the simplest upwards.
Monoterpenes………..C 10 H 16
Sesquiterpenes……….C 15 H 24
Diterpenes……………C 20 H 32
Sesterterpenes………..C 25 H 40
Triterpenes……………C 30 H 48
There are enormous amounts of terpenes synthesised in plants. They include the basis for steroidal molecules, as well as carotenoid pigments and rubber, but in terms of volatility, only mono and sesqui-terpenes are of interest for now.


These are by far the biggest group of volatile oils. The names of many common examples below will become more familiar as we continue the journey through the materia medica:- anethol, borneol, camphene, camphor, carvacrol, carvone, cineol, citral, citronellal, cymene, cymol, fenchone, geraniol, limonene, linalool, menthol, menthone, nerol, phellandrene, pinene, thujone, thymol.

They are the largest group of terpenes in the plant kingdom, but only a few are volatile-notably the azulenes, bisabolol and farnesene from Chamomile and Yarrow, whilst many others are very bitter tasting; notably found in the large Dandelion family and others. Some are anti-inflammatory Monoterpenes have anti-septic properties. Compared to the strength of phenol, the anti-septic capacities of some common monoterpenes are as follows:

Carvone                            x 1.5   strength
Citronella                          x 3.8         “
Menthol                             x 4.0         “
Linalol                                x 5.0        “
Citral                                  x 5.2        “
Geraniol                             x 7.1         “
Thymol                               x 20.0       “

Some monoterpenes have fungicidal and anthelmintic effects eg thymol, whilst others have a circulatory stimulating rubefacient property, including menthol, camphor and borneol. For this they are regularly included in ointments and linaments, whereas internally, through utilising the same properties, they form the basis of an expectorant action; examples are cineol from Eucalyptus (Eucalyptus globulus), pinene from Angelica (Angelica archangelica) and pinene-borneol and others from Thyme (Thymus vulgaris). It is known that this action is also as a result of reflex stimulation of the stomach lining.

Other monoterpenes act on the nervous system. Carminative herbs act through local reflex of nerve endings in the gut, producing a spasmolytic action. Furthermore, some monoterpenes including citral, limonene, citronellal and citronellol have appreciable sedative activity, citronellal being most potent, whilst also exhibiting spasmolytic action comparable to the morphine alkaloid papaverine.

Sesquiterpenes have a higher molecular weight and are therefore less volatile and less associated with volatile oils. Some of them are volatile however, including the azulenes from the Asteraceae family, in Yarrow and Chamomile respectively. The azulenes do not exist in the plant itself but are a product of stem distillation. They will be found therefore in your cup of infused herbal tea should you have infused the material in a vessel with a lid on!

The azulenes are notable as anti-inflammatory’s and anti-spasmodics, reducing tissue reactions of a histamine induced nature as well as calming the nervous system. The actions on the C.N.S help anxiety, nervous tension and headaches and are coupled with assisting peripheral visceral tension- in muscles and surface tissues. They are also noted for being strongly anti-septic as well as exerting a reduction of the anaphylactic shock effect due to allergic responses. For this reason they are well indicated for Hay fever, allergic asthma and allergic excema.

Bisabolol is another constituent of Chamomile essential oil, however this one occurs naturally. It can reduce the amount of the enzyme, pepsin, secreted into the stomach wall without changing the amount of stomach acid produced. This seems to suggest a particular affinity with pepsin activity. The enzyme pepsin is secreted in the stomach in order to break down proteins, especially animal based ones.

There are numerous other components of volatile oils and it has already been noted how very small molecules can exert significant pharmacological activity.  Different combinations of plant constituents produced by the aromatic plants are exceedingly complex. In fact scientists are only just beginning to discover a handful of the numerous effects.

Non-terpene volatile oil constituents include: anethole, found in Fennel (Foeniculum vulgare) which comprises upto 90% of the vol oil extracted from Aniseed (Pimpinella anisum). Others, such as cineole, are notably found in the Eucalyptus (Eucalyptus spp)and cajaput oil (Melaleuca leucadendron); apiole, from Celery (Apiens graveolens) and Parsley (Petroselinum crispus); myristicin from nutmeg (Myristica fragrans). These, similar to other volatile components, have carminative, anti-septic, expectorant and circulatory stimulant qualities.

Many members of the Allium family contain volatile sulphurous substances. These include mono and disulphides found in Garlic, Onions (Allium cepa) and others. Some Brassica’s, including Radish (Rapahnus spp) and cabbage (Brassica oleraceae) also contain them. They are responsible for the acrid, pungent aroma common in these plants.

In general, the actions of volatile oils can be summarised accordingly:


Because of their fat-soluble nature, volatile oils can easily pass through fatty membranes into single cell organisms where they are thought to disrupt cellular mechanics. This solubility also enables volatile components to be easily distributed throughout our bodies, exerting their antiseptic qualities. As well as this, volatile oils trigger increases in white blood cell production  (leucocytes), providing a two-fold action of a direct effect whilst enhancing the body’s own natural defence systems.


Tissues that volatile oils come into contact with are stimulated in different ways. Effects such as vaso-dilation and general increased circulation are of importance. When nerve endings in the G.I.T are stimulated they produce increases in gastric juice secretion, salivation and appetite. Peristalsis is improved whilst flatulence and colic are relieved. When discussing carminative herbs, we are generally talking about herbs with volatile oils exerting effects just mentioned.


Volatile oils will reliably reach nerve endings and tissues as a result of their fat solubility. Their notable effects on the C.N.S include tranquilizing (dampening down of messenger molecules). Peripherally, anti-spasmodic effects are noticeable. It has often been found that relief in digestive conditions such as dyspepsia are through relaxation of internal tissues, whereas asthma can be greatly assisted by relaxation of the bronchioles, which can feedback to relieve tensions often found in the C.N.S. It is worth remembering then that tensions can be arrested and readily soothed as much ‘from the neck down’ as by any sedative or relaxant effect experienced through the mind.


Resins are a complex group of solid and occasionally liquid substances. They are characteristically insoluble in water, but soluble in alcohol, ether and chloroform. They are often produced in a number of plants as a self-defensive, protective mechanism, either as a result of injury or pathogenic attack, whilst in others as a matter of course during flowering.

Essential resins are a mixture of resin alcohols, acids and phenols, esters and other inert substances. These can be fashioned with essential oils and gums to create the ‘oleo-resins’ and ‘gum-resins’, or even compounded to create ‘oleo-gum-resins’. Pine (Pinus spp) produce well known sticky resins. Cannabis (Cannabis sativa) produces an ‘oleo-resin’ whilst well known oleo-gum-resins include myrrh (Commiphora molmol) and frankinsense (Boswellia spp). Medicinal effects of the resins are anti-septic and stimulating phagocytosis.


Derived from the latin word for soap- ‘sapo’, the name bestows the principle actins of these molecules, to exhibit frothiness in solution. They are the major constituent within Soapwort (Saponaria officinalis), a plant whose roots have been used as a soap substitute by country folk. Saponins are high molecular weight compounds which can be loosely and usefully divided into two skeletal groups:

  • steroidal saponin skeletons
  • triterpenoid skeletons.

They were originally known medically almost exclusively for their haemolytic (red blood cell destroying) properties. As with any detergent they are toxic to all animals if intravenously injected. It is for this reason that plant extracts are not administered in this way as most plants contain saponins to a lesser or greater degree. Saponin containing plants have often been employed as arrow poisons and fish poisons.

However, it is the property of the whole molecule that is toxic. As mentioned elsewhere, most plant molecules are usually attached to a sugar unit (called glycosides). When cleaved, the sugarless portion is known as the aglycone. When saponins are ingested, the whole molecule is quickly hydrolysed in the stomach, leaving the pharmacologically active aglycone. This sugarless saponin does not confer haemolytic actions. However, Fish and other cold-blooded creatures are always poisoned by saponins, in any form.

The steroidal form of saponin is found both in the monocotyledon families of plants (including the large Lilliaceae together with the various Grass families) and the dicotyledons (majority of plant families). Notable are foxglove (Digitalis purpurea), fenugreek (Trigonella foenum-graecum) and various members of the well-known Solonaceae family, home to the tomato (Lycoperiscon esculentum), deadly nightshade (Atropa belladonna), henbane (Hyoscyamus niger), potato (Solanum tuberosum), tobacco (Nicotiana spp) and datura (Datura stramonium).

Steroidal saponins have structural similarity with steroid hormones, cardiac glycosides and Vitamin D. They are the framework for modern production of synthetic hormones. Contraceptive hormones such as dioscin were first synthesised from an extract from the Yam (Dioscerea species).

Tri-terpenoid saponins are rare in the monocots but are widely found in di-cots. The steroidal nature of saponins are thought to be through interaction with the body’s steroid receptors or potentially are precursors to steroid hormones. This was proposed by researchers working on the false unicorn root (Chamaelirium luteum) that discovered the saponins act on ovarian function in women.

Many saponins act on the respiratory system, (possibly by reflex action, as a result of their overall emetic effect if taken in bulk.) At sub-emetic doses they stimulate expectorant activity, notably Mullein (Verbascum Thapsus) and Liquorice. Some can settle the stomach, aiding the absorption of minerals. (Oats are a suitable saponin containing remedy for this). Others are anti-inflammatory, such as the cornsilks from Sweetcorn (Zea mays), Silver Birch (Betula pendula) and Figwort (Schrophularia nodosa).

In China there has been a reputation for taking saponin-containing ‘King remedies‘. These seemingly harmonising tonic herbs were for a long time discredited by western Doctors, but recent research into well-known saponin-containing remedies such as Liquorice, Angelica (Angelica archangelica) and Ginseng (Panax ginseng), has shown many benefits these herbs can offer, reportedly due to saponin /steroidal receptor activity. These remedies are now widely known for their effects they have on metabolism and with it, sustaining of energy levels and moods.

Ginseng is one of a group of herbs now known as the adaptogens. In simple terms this means they are viewed as being state-specific, i.e. they will have different actions dependent on whatever state the body is in when the remedy is ingested. Change is presumably wrought either by chemical or other hormonal messengers enabling these remedies to seemingly adjust the body’s internal homeostasis rather than correct any specific faults.

Cardiac glycosides
Alongside the opiates, these are the most studied of all the plant constituents. Once again, the active pharmacological ingredient is the aglycone. The steroidal aglycones from which the cardiac glycosides are built reportedly have very similar properties to steroidal saponins, and are found together in many plants.

Cardiac glycosides were most famously extracted from a recipe for ‘dropsy’ (which had included foxglove as its principle active component) during the latter part of the 18th century by the apothecary physician William Withering.

The use of these molecules has now become well established for preventing the unpleasant symptoms of heart failure, which include the aggregation of fluids, retained by the force of gravity in the ankles, legs and abdomen as well as a shortness of breath when lying down.

As their name suggests, the cardiac glycosides act on the heart muscle. They reportedly affect the potassium / calcium balance across the myocardial membrane, giving rise to cellular potassium loss. There is a relative concentration of sodium in the cell, relative to potassium loss and this effect is repeated throughout other cells in the body. The effects of cardiac glycosides will vary with the condition of the muscle cells and the dosage of the medication. The random use of these potent drugs cannot be recommended by clinically untrained people.

Cyanogenic glycosides.
These are one of the primary constituents responsible for the aroma and flavour of bitter almonds and are common in many stone fruits of the Rosacea family such as Peaches (Prunus persica), Apricots (Armeniaca vulgaris), Nectarines (Prunus persica var ‘nectarina’),and Hawthorns (Crataegus spp). Cyanogenic glycosides are also found in the Elder tree (Sambucus nigra) and Clovers (Triolium spp). They take their name from the breakdown products after hydrolysis. The aglycone converts to prussic acid (also known as hydrogen cyanide), therefore in any quantity these compounds are very toxic.

However, by using remedies with very small amounts of cyanogenic glycosides, noticeable anti-spasmodic and sedative effects are produced, as in the wild cherry (Prunus serotina). They also have an effect on the parasympathetic nervous system, slowing the heart rate and improving digestion. The lungs excrete these molecules quickly so regular topping up on foods containing them seems logical.

Mustard oil glycosides
Otherwise known as the glucosilonates, these molecules are found in the Brassica family (Cruciferaea) . More than 60 compounds have been isolated and they are responsible for the pungent aroma of members of this large family. As with many plant constituents mentioned here, the aglycone is the active pharmacological substance following hydroylisis in the gut. Molecules of interest include: the irritant isothiocynates, thiocynates, nitriles, and thiourethanes.

Plants containing mustard oil glycosides are used mainly to increase blood flow to membranes they contact. Hence their use as rubefacients as they increase local blood flow. A classic example of their traditional use is the mustard footbath. They are also known to be goitrogenic (depressed thyroid function), and for this reason, people with hyperthyroidism are advised not to consume too large a quantity of brassicas.

As a group, the array of acrid molecules are mainly known for stimulating the circulation due to their irritant effect; toning, slowing the heart rate and improving digestion, whilst the oils found in Ginger (Zingiber officinale), Garlic and Horseradish (Armoracia rusticana) are easily excreted from the lungs, effectively acting as an anti-septic disinfectant, whilst warming and lifting mucus from the airways. This helps explain their repeated use in cases of bronchial infection and catarrh.

These are central components within a herbal approach to treatment. Most plant remedies have at least a small amount of bitterness. This taste sensation is behind much of the face pulling that often follows consuming them! The range of bitter principles in plants amounts to the largest and most diverse group of plant constituents. Bitters all have in common the ability to stimulate the bitter tasting cells in the mouth, which in turn stimulates an increase in calcium in the cells. (This element plays a role, in both animals and plants, as a cellular relay molecule of hormones and other bio-chemical reactions producing physiological change.)

Bitters are now known to only work through the bitter tasting receptors in the mouth and have no effect if taken as a capsule. Following the change in calcium levels, a hormone, gastrin is released. This has a number of functions including:

  • Increasing gastric acid secretions
  • Stimulating pepsin secretions
  • Stimulating pancreatic digestive secretions
  • Intestinal juice production
  • Hepatic bile flow,
  • Hepatic bicarbonate production,
  • Insulin derived glucagon secretions,
  • Toning the muscle of the lower oesophageal sphincter,
  • Toning the muscle of stomach wall and small intestine
  • Cell division and growth of gastric and duodenal mucosa
  • Cell division and growth of the pancreas

These are probably the most studied and some of the most potent and toxic plant products. Most plants have at least some alkaloids in them. The first alkaloid extracted was morphine in 1805. Care is advised when taking remedies with appreciable amounts. Typically not soluble in water, but able to dissolve in alcohol the alkaloids are therefore prone to differences in both absorption and bio-availability (amount of time a remedy is active before elimination) dependent on the menstruum or solvent used. Chemists have divided the alkaloids into various groups in order to reflect their different origins or biosynthetic pathways within plants.

Pyrrollidine alkaloids
These come from the base amino acid ornithine. They act on the parasympathetic nervous system, blocking nerve activity. Included here are cocaine, hyoscyamine, scopolamine, hyoscine and atropine. Many Solanaceae plants including henbane, datura, belladonna and bittersweet (Solanum dulcamara) contain these alkaloids.

Pyrrolizidine alkaloids
These have a reputation for notable toxicity linked with liver damage. These alkaloids are another group emanating from the amino acid ornithine, found in ragworts (Senecio spp) coltsfoot (Tussilago farfara) and the borage tribe, most famously within comfrey (Symphytum officinale).

This group of alkaloids are widely reported in many crass herbal reference books as being simply toxic, and therefore outright dangerous. Within this whole class of compounds, only the compounds with ‘carbon skeletons’ containing unsaturated bonds (between positions 1,2 if you are a chemist) are hepatoxic.

Possible consequences of sustained over-consumption can result in veno-occlusive disease of the hepatic vein and increased risks of hepato-carcinogenic reactions. Their effects are apparently accumulative. However, some latest research shows these compounds to be relatively labile and not the danger first imagined.

Indole alkaloids
These molecules are a group founded on the amino acid tryptamine. Included here are the mood molecules, serotonin, adrenaline and noradrenaline as well as the tranquillizing alkaloids found within the various passionflowers (Passiflora spp) Also of note are the products of ergotamine, such as Lysergic acid diethylamide (L.S.D) and the central nervous stimulants strychnine, johimbine and psilocybin.

Quinoline alkaloids
The anti-malarial drug quinine, documented to have originally been derived from Cinchona ledgeriana and now extracted from a number of Artemisia species gives its name to this group of molecules which also includes the isoquinolines. They are constructed from the amino acid phenylalanine. Notable extracts include mescaline from Lophophora williamsii, the opiate alkaloid papaverine and the compounds berberine and hydrastine from Berberis species.

Purine alkaloids

These are derived from the nucleotides adenine and guanine and act on the nervous system, prolonging the life of many secreted hormone-like substances including adrenaline. Included in this group are the xanthine alkaloids caffeine, theobromine, theophyllene and aminophyllene from coffee (Coffea Arabica), cocoa (Theobroma cacao) and the Tea plants.