Wild Plants and Medicine by Gerald Dawe

CAUTION: PLEASE CONSULT YOUR MEDICAL DOCTOR BEFORE INGESTING ANY DRUGS DERIVED FROM ANY OF THE PLANTS MENTIONED IN THIS ARTICLE.

Introduction

Plants are, in many ways, like wonderful kitchen or medicine cabinets filled with attractive things. They contain food, sometimes what may be regarded as hazardous or even poisonous (not that these should be allowed in the kitchen!), and mixtures of the most extraordinary ranges of chemicals, some of which can act beneficially on the human physique and other which may have a detrimental effect.

There is magic and wonder here too. For a great many of our wild species, almost nothing is known, still, regarding their chemical make-up, beyond the bare bones of the fact that most contain carbohydrate, fat protein and chlorophyll (the chemical which makes plants green). Also, amazing mysteries still abound as to many chemical's exact function or impact, or interaction with each other.

In many cases, in all probability, the ancient herbalists knew more than we do today, at least about the benefits of using a various wild species. Their connections with nature were of a much more profound order. However the history of the use of wild plants in medicine is certainly a chequered one.

A Very Brief History

Wild plants have been used for treating human ailments for many thousands of years. Evidence of the remains of medicinally active specie within archaeological sites, dating to c.1,000 BC shows this to almost certainly have been the case.

In more recent times, the writings of English herbalists have been influential. These were generally derived from Continental, often Mediterranean sources, and contained relatively few observations new to the British Flora. For example, John Gerard's Herball of 1597 fits neatly within this category (Vickery, 1995). In 1578, Richard Bagge of Hereford was already making a living out of producing and selling rosalus (sundew-Drosera) angelica watur and minta romana (spearmint) around the county. The latter plant was used for hastening birth and there is some evidence that it was even used for abortion.

Mid-17th century herbalists often held to the Doctrine of Signatures. This was the notion that the external appearance of a plant hinted at its God-given use. Thus lungwort was used for inflammation of the lungs, gromwell with its stone like seed for removing kidney stones, and possibly figwort for dealing with boils (the root of the figwort has many boil-like swellings).

By the end of the 17th century the Doctrine of Signatures was coming under attack from developing science. When the latin bi-nominal nomenclature (e.g. Quercus robur is the latin name for Oak) system became adopted in the 18th century, following the publication of Species Plantarum (1753) and Genera Plantarum (5th edition, 1754) by Linnaeus, it was common knowledge that many plants were valuable medicinally. This is even indicated within the name. Thus, if one looks at the second part of the latin or scientific name accompanying a plant, and it is officinalis or officinale, this means 'medicinal'.

Equally, however, there are many plants of proven medicinal use which do not have this name attached. Nevertheless, here are some Herefordshire officinale plants.

What are, or were, their medicinal uses? Well, as a simple catch-all, one can say that many were used as an antidote to scurvy (Vitamin C deficiency). Indeed, an early issue of the Hereford Journal contains advertisements including one for "Dr Mardon's scurvy drops" indicating that it was a public concern, although not necessarily a major problem in Herefordshire. There are other subtleties here too, which one can explore. For example, comfrey was used for poultices. Why the need for purgatives? Parasitic worms such as tapeworms were a common problem, and in the case of other disorders, it was simply thought that administering  'purge' (ingesting something to make yourself sick) was beneficial.

In the 19th century herbal remedies became widely exploited by people, with varying underlying justification for them. As the 1867 Annual Report of the Hereford Medical Association said at the time " Quackery is hydra-headed, and no sooner is one form exposed, than another shoots up, and as readily as ever, finds its victims in poor, weak, gullible, human nature" (Langford, 1958).

What is the situation now? Hopefully one of relative harmony between conventional medicine and users of herbal remedies, with both contributing to the well-being of society, and complementing each others' therapies. The dialogue has certainly started.

What's your poison?

Which of the plants that have potential medicinal uses and which are worth avoiding? First of all, there is increasing evidence that many ferns contain chemicals which can. under certain conditions, initiate stomach cancer. So: while they are excellent to plant, and often very beautiful to look at in the wild, it is best not to risk ingesting their complex mixtures of chemicals, which may be hazardous. Nevertheless, in extremis, the dried stems of horsetail (Equisetum spp.),  plant closely related to ferns, has been recommended as a 'vulnerary' for use against consumption and dysentery.

Perhaps related to this phenomenon of potential toxicity are those plants which contain large amounts of tannins. What o tannins look like? Well, if you have ever seen oak apple gall, or marble gall, on an oak tree, you will have seen tannins. Many galls on British oaks contain between 20-70% of tannins (more usually it is 20%) and some galls are even commercially important in leather tanning. What are tannins? They are chemicals which bind with proteins and stop their absorption in the gut. Their function in many trees and shrubs is thought to be to deter caterpillars from completely eating their leaves.

Tannins are especially common at high levels in plants which are common everywhere. Why? Because plants that are obvious, are eaten. Over thousands of years, many such plants built up resistance to this form of damage, in the form of tannins. These plants are known as 'apparent' plants: species which tend to dominate the landscape. By contrast, 'non-apparent' plants such as some wildflowers, tend to be less obvious, and have less need for tannins. For more information, read the classic paper ny Feeny (1976) on 'plant apparency'.

While tannins undoubtedly make trees and shrubs a difficult meal for many caterpillars, the evidence of their effects on human health remains somewhat contradictory. For example, it is widely believed that the English habit of drinking copious amounts of tea in cities, via the inhibitory effect of tannins in microbes, led to huge health benefits for the human population during the 19th and 20th centuries. However, there is some marginal evidence that tannins, under certain circumstances, can initiate gut cancer. Nevertheless this author has been ingesting copious amounts of plant phenolic chemicals (more commonly known as tannins) contained in cups of tea, as he has been penning this article. He thinks it is worth the risk. If you switch to green tea, then, of course, you will be ingesting substantial amounts of 'flavan-3-ols', another somewhat obscure chemical. To sum up, plant tannins have been widely recognised for their pharmacological properties for some time, and have been employed medicinally, especially in China and Japan.

To give some local examples of the use of plant tannins in medicine, the ripe, tannin-laden fruit of the hawthorn (Crataegus spp.) is often used as an infusion, cardiac tonic and hypertensive. According to Haslam (1989) it is 'one of the best known tonic remedies of heart and circulatory system. Used in the treatment of high blood pressure and angina'. As ever, hawthorn is also employed 'as an astringent and diuretic'. The leaves and fully-opened flowers of meadowsweet (Filipendula ulmaria) are dried and used as a good digestive remedy. The implicated tannin is rugosin-D, and the metabolites tellimagrandin-1 and -2 (Haslam 1989). It is also used as a good diuretic.

Hawthorn

Other Poisons

One of the classic medicinal wild plants which grows commonly throughout almost all of Herefordshire, is foxglove (Digitalis purpurea). A complete annotated facsimile of William Witherings's early 1785 work into the medicinal uses of foxglove, will be found in Aronson's (1985) valuable work, which updates the cultural and medicinal view of Digitalis since that date. William Withering MD stumbled across the potential uses of the plant whilst in Birmingham. Foxglove is very poisonous, yet it contains invaluable glycosides which are used in medicine. Those of the wild plant (D. purpurea) are technically known as :digtalinum verum, digitoxin, gitoxin and purpurea glycosides (desacetyldigilanides) A and B, together with strospeside (Aronson, 1985).

In the Middle-Ages foxglove seems to have been used as a cure-all, and (poisonous) foxglove tea was drunk in the early 19th century. However, the effectiveness of its component glycosides in regulating heartbeat gradually became known,a nd they are used today in cases of people with heart problems, the chemicals involved being too complex to synthesise artificially. Semi-synthetic cardiac glycosides are now becoming increasingly available, but rather like Digitalis, they are not free of occasional toxic side-effects. Finally, foxglove is also a very powerful purgative and diuretic.

Alkaloids, another group of chemicals, are found very frequently in certain wild plant species. Yew (Tasus baccata) is extremely poisonous, widespread in Herefordshire, and contains the very toxic alkaloid taxine. Yews are, however, now being harvested commercially as a source of anti-cancer drugs. St John's Wort (Hypericum perforatum) is again common and widespread in Herefordshire and contains a wide range of chemicals including glycosides (rutin and hypericin), tannins (the flowers contains as much as 16%), catechol, an essential oil and resin. It has been called the 'prozac' of the plant kingdom and is now firmly on the medical agenda as a treatment for mild depression. However, it has been shown to interfere with various other prescription drugs including the above mentioned digitoxin and also chemical contraceptives, so it must be taken with care.

Yew

Local Investigations

Probably the wisest advice that can be given regarding wild plants is never to ingest them, but rather, learn to recognise them so that one cane build up one's own knowledge of putative past pharmacological usage within Herefordshire. For example, why is it that common gromwell (Litjospermum officinale) is found both on disturbed ground at the hill fort above Fownhope and near to British Camp, that very famous hill fort on the Malverns? Could it be that Iron Age people wanted a local treatment for kidney stones, or more likely something of use as a contraceptive, and this herb has simply persisted ever since. Unlikely? Very probably. But it is possible for such plants to persist for thousands of years in localities where they have been used,. Perhaps however, its presence merely indicates skeletal limestone soils. But by looking at medicinal herbs, and their occurrence in Herefordshire, important clues may be revealed about past practices, as well as about their continuing habitat preferences.

Gromwell

Of other plants occurring frequently in Herefordshire, mistletoe (Viscum album) deserves a mention. This has a riverine distribution, and is strongly associated with the River Wye in Herefordshire. Mistletoe has been used in treatments for cancer. But like so many anti-cancer drugs, its components are highly toxic. Mistletoe contains 'lectins' - these are ribosome-inactivting proteins. Three have recently been extracted by Hideaki Niwa from Birbeck College, London. The lectins are known as ML1, ML2 and ML3. ML1 is regarded as the most biologically active, and it is also synonymous with 'viscumin'. Paradoxically, it is at least partly due to the extreme toxicity of ML1, that it is thought to stimulate the immune system. Mistletoe has undoubtedly been used in medicine since ancient times, but it can cause irreversible toxicity and liver damage. Right: Mistletoe growing on a fruit tree

Conclusion

The medicinal properties of wild plants within Herefordshire, as for those of the rest of the UK, remain, as yet, not fully known. There is a healthy respect required for the chemistry of wild plants, which when administered have the potential to either cause sudden death, or to poison, in some cases, irreversibly, or indeed, to lead to cures. They are wonderfully paradoxical. There is clearly a very careful balance to be struck. The intriguing and relatively frequent phenomenon of horses and livestock becoming addicted to poisonous plants found in their pastures needs mentioning as a final cautionary note. It is evident that, in a rather similar fashion, wild plants, through frequent use, can build up toxic effects over the long-term in human beings, who continue to take them unawares, or even fondly. Hence the strong advice to take medical advice before administering them. Yet at the same time, we remain absolutely dependent on our precious storehouse of wild plants for the ultimate source of almost all of our medicines. The medicinal uses od wild plants thus remain ultimately paradoxical, and their underlying complexity, wonderful and often unacknowledged.

(Gerald Dawe is at the School of Earth Sciences and Geography, Faculty of Science, Kingston University.)

Bibliography

Aronson, J.K. (1985). An Acount of the Foxglove and Its Medical Uses, 1785-1985. Oxford University Press.
Feeny, P.P. (1976). Plant Apparency and Chemical Defence. Recent Advances in Phytochemistry, 10, p.1.
Grigson, G. (1975). The Englishman's Flora. Palasan, St Albans.
Haslam, E. (1989). PLant Polyphenols: Vegetable Tannins Revisited. Cambridge University Press.
Langford, A.W. (1958). Some Herefordshire Medical History. Transactions of the Woolhope Naturalist's Field Club, XXXVI, 56-66.
Vickery, R.(1995). Oxford University Press, Oxford Dictionary of Plant Lore.