|
| |
Natural Drugs and Modern Medicine
From: Cambridge University Press
| By:
John King |
EDITOR'S INTRODUCTION |
Western society tends to emphasize the efficiency of manufactured drugs over the ostensive healing power of "natural remedies." But in doing so it is ignoring a long and beneficial relationship that has existed between humans and the plant kingdom. Internationally respected scientist John King looks at some of the most common drugs, both remedial and "recreational," and suggests that modern medicine has much to learn from the world of nature. |
 lant chemicals are used in three main ways in Western medicine nowadays: some are used directly in medicines and medications; others are analyzed so that their exact chemical structures are known and then ways are found to manufacture them artificially rather than just relying on the natural source, which may be rare, anyway; and finally, they may not be used directly in treatments at all but as tools to help us develop new drugs. For example, a plant may be found which has in it a compound which has only a mild effect on some disease. But, by extracting and working out the structure of this compound, and manufacturing it artificially, we can then change its structure in several different ways to see if we can improve its effectiveness or gain new insights as to how to design a more effective drug of a similar type. |
Very few types of medicinal plants have remained in favor for even so much as 100 years. Some--opium, cocaine, marijuana, and quinine are four examples--have survived the centuries but most are much more recent. |
Poppy derivatives
One of the most renowned botanical drugs is opium from a species of poppy native to Asia Minor. Legends about opium are recorded in Egyptian hieroglyphs and Homer in his Odyssey speaks of nepenthe, a substance that would "lull pain and bring forgetfulness of sorrow." At the same time, others warned of the addiction to opos, the milky sap of the poppy capsule. Many down the centuries have written with fascination of this great analgesic. |
The main attributes of opium are mostly due to the morphine it contains. Yet, morphine is just one of some 25 medically interesting compounds found in the milky latex exuded from the immature seed capsules of the poppy when it is cut open. Morphine takes its name from the Greek god, Morpheus, the bringer of dreams. The Greeks regarded sleep as the great healer; the opium poppy, therefore, was celebrated in their art, literature, and religion. Long before the ancient Greeks, as far back as 8000 years ago, there is evidence of small opium balls being eaten or mixed with wine to induce sleep and relieve pain. In nineteenth century Britain and elsewhere, laudanum (now called tincture of opium) was regularly prescribed by physicians, causing widespread addiction to the drug. |
In the latter half of the nineteenth century, chemists began to tinker with the morphine molecule to try and make a compound that would be more effective than the natural product as well as less addictive. By the end of the century, German chemists had, indeed, found a more effective painkiller made by modifying morphine. Its name? Heroin! |
Codeine, another of the compounds found in the latex of the poppy (but only one-fifth as strong as morphine) is still widely used as a household painkiller, especially in cough medicines. Incidentally, heroin once was regarded as a much more effective cough suppressant than codeine and was openly sold in cough medicines, in North America at least, until near the end of the second decade of the twentieth century. It is suggested that there may have been as many heroin addicts in New York City in the early 1900s as there are today. Most of them, however, were children treated for coughs, often the result of tuberculosis in those days. |
Coca and marijuana
Hospital patients everywhere have benefited greatly from the leaves of the coca bush (Erythroxylum coca) which have provided some of the most valuable and widely used anaesthetic compounds in use today. The leaves contain some 14 different ingredients, including cocaine which itself is used as an anaesthetic but which also has been used as a blueprint for the development of a number of artificial painkillers such as procaine and novocaine. |
Besides giving us cocaine, the coca leaf is famous as the stimulant used by Andean porters and laborers who, reputedly, can work with superhuman endurance for days with little or no food if they chew coca leaves. When chewed with a little lime or plant ash, active compounds are released from the leaf which stimulate the nervous system enhancing muscle potential, increasing stamina, depressing hunger, and relieving pain. Distances in the Andes can be reckoned in "cocadas," the distance that can be traveled on one coca leaf chew. |
Interestingly, since the South American Indians do not take in cocaine alone, but only as one ingredient of many in the coca leaf, they do not suffer the addictive and mind-altering side effects we commonly associate with the pure compound. Why this is so remains a mystery. Pure cocaine we know is dangerously addictive whilst cocaine in a crude mixture taken directly from the coca leaf appears not to be so to nearly the same extent; just one more example that there is sometimes more to natural plant medicines than we give credit for. |
 One more ancient drug that today we judge to be too dangerous for general use, described by the Chinese nearly 5000 years ago, is marijuana (also known as hashish, ganja, or kif) made from the resinous oil of the cannabis plant. Experience seems to show that marijuana is not particularly addictive and less habituating than alcohol or nicotine. Hashish, the unadulterated resin from female cannabis flowers, is most famously associated in folklore with a curious Mohammedan sect, the "hashishins" (whence "assassins"), whose avowed religious purpose was to murder "enemies of the faith" in order to enter paradise. Hashish figured prominently in arousing their religious fervor, and the sect numbered in the tens of thousands in Syria and Persia until they were violently and forcefully suppressed by the Tartars in the thirteenth century. Arguments for and against the legalization of marijuana continue to the present day, so far without final resolution. |
Quinine and malaria
Of course, not all drugs derived from plants are as currently socially unacceptable as the three discussed so far. One of the most remarkable of those in the "approved" category is quinine. A small, attractive evergreen tree with glossy leaves and fragrant pink or yellow flowers provides the world with one of its most precious medicines. This drug, found in the bark of several species of the cinchona tree, which are native to the humid forests high in the Andes of South America, is still the foremost cure for malaria, a disease which affects over 100 million people a year. |
This antimalarial drug was used by the Andean Indians long before Europeans discovered the, so-called, New World. The conquistadores and the Jesuits brought it to Europe from South America at the beginning of the seventeenth century. However, the entrenched and powerful medical professionals in Spain and elsewhere ridiculed and rejected the cure since they were making significant financial gains by treating patients suffering from malaria with their own patent remedies. Then, Robert Talbor, a British apothecary who lived and practiced at the end of the seventeenth century, successfully cured King Charles II of the "ague," as malaria was then known, with bark from a Peruvian cinchona tree. From then on this miracle cure was elevated to the center of attention in Europe. |
By the second decade of the nineteenth century, quinine itself had been isolated by French doctors and named from the Amerindian word for the cinchona tree, quinaquina (which means "bark of barks"). The demand for the drug then rose so dramatically that by the mid-nineteenth century, wild cinchona trees were being exploited to extinction. Even their roots were being dug up and stripped of bark. |
Fortunately, this vital plant component in the world of medicines was rescued by a British seed collector, Charles Ledger, who sent some cinchona seeds to Europe. The British government declined to buy the seeds; however, they were purchased by Dutch authorities for about six pounds sterling. From 450g of these seeds, the Dutch grew 12,000 cinchona trees in their colony, Java, and for the next 100 years controlled nine-tenths of the world's supply of this vital medicine. The original purchase of seed by the Dutch has been described as the one of the best investments in the entire history of commerce! |
The world monopoly in quinine supply by the Dutch was broken by the World War II invasion of Java by the Japanese. Seeds were flown out of the colony by the Dutch at the last minute but this did not help the troops already serving in the Pacific theater of conflict. The USA, instead, sent a team to Columbia where nearly six million kilograms of dried bark were collected for use throughout the war. |
Synthetic quinine was finally manufactured in the USA towards the end of World War II and from then on the demand for the natural product declined. Interestingly, however, in the 1960s, certain strains of the malaria parasite were found which were resistant to this synthetic form of the drug. There are today areas of the world where the synthetic drug is not used at all because of this resistance. But none of the strains of malaria parasite is yet resistant to natural quinine. The natural product (often called "totaquine") has in it four antimalarials, quinine among them, not just one as in the case of the synthetic drug. This seems to be another outstanding example of a natural medicine being superior to an artificial copy, similar to the case of the coca leaf versus pure cocaine; both are examples where a mixture of natural products out-performs the purer, but synthetic counterpart manufactured in the Western medical fashion. |
Aspirin
Arguably, the most widely used drug world-wide is aspirin. Though the compound today is made synthetically, it was substances extracted first from the white willow (Salix alba) and later from the herb, meadowsweet (Filipendula almaria as it is now known), which gave to chemists the blueprint for making this universal curative. |
The willow has a long-held reputation as a painkiller. The observation that willow leaves, as they moved in the wind, seemed to resemble the trembling of a fever patient led to the ancient use of infusions of white willow bark as a treatment for fevers. Yet further back in history, as early as 2000 years ago, at the time when Dioscorides was compiling his De Materia Medica, the willow was also being used to treat gout, rheumatism, toothache and earache, as well as headaches. |
Eventually, it was found that the active ingredient in meadowsweet, salicylic acid, was more effective than the related chemical compound first extracted from willow. By the end of the nineteenth century, German chemists had discovered that salicylic and acetic acids could be combined to produce acetyl salicylic acid (the now familiar ASA) which proved more potent than anything that had gone before in relieving all kinds of pain. The trade name for aspirin, thus, was derived from the nineteenth century Latin name for meadowsweet, Spiraea ulmaria, not from willow. The medical conditions that appear to be helped by aspirin seem endless; the list continues to grow every year. Yet, even after decades of intensive investigation, we still have little idea why the compound is so effective in so many ways. |
Hormones and steroids
A somewhat more recent major discovery of a plant compound of medical interest than those discussed so far occurred in the 1940s. One of our best known forms of birth control, "the pill," is derived from diosgenin, a compound found in high quantity in yams, that belong to a family of climbing forest vines. When American chemists showed how diosgenin could be used to produce male and female hormones, the sexual revolution which is still going on today was launched. |
The same group of plant chemicals from which diosgenin comes also contains compounds that are the starting material for other important families of drugs used in the world today. Alongside oral contraceptives we can place cortisone and hydrocortisone as well as sex hormones and the anabolic steroids. The current widespread abuse among athletes of some of these products should not detract from the fact that many of them have widely beneficial, legitimate medical value. |
Garlic
We tend to think of garlic more as a condiment than as a medicine; we should consider it as both. As a natural antibiotic, garlic has been used in many areas of the world to treat, especially, nose, ear, chest, and throat infections. For the early treatment of colds and flu, cloves of garlic kept in the mouth is a long-standing folk remedy. Sufferers from colds, flu sinus congestion, whooping cough and bronchitis as well as high blood pressure, acne, asthma, and even diphtheria have all benefited from the use of garlic. |
As early as 5000 years ago, Mediterranean and Far Eastern peoples were already using garlic. The Greek physicians, Hippocrates and Galen, prescribed garlic for various infectious diseases; Dioscorides used it to treat worms in soldiers of the Roman army. |
The active ingredient of garlic is called allicin, a compound which has a distinctive smell and which acts by literally suffocating infectious bacteria. Nearly all the members of the lily family related to garlic, such as onion, leek, and chive, also have some form of medical value. Onions in particular, other than garlic, have been used for more than 5000 years and were for a long time highly prized for their medicinal properties. They are said to stimulate insulin production, lower cholesterol levels in the blood, promote healing of wounds, and suppress allergies. Today, we take them for granted and use them only in cooking, not especially as curatives. |
Current trends
Today, a major focus for the development of new plant medicines is the rainforests of the world. There, plants are in close competition with one another for survival; for space, light, and nutrients. Rainforest plants also must protect themselves from attack or injury from a host of insects and other voracious predators. In order to survive in this cutthroat world, many types of plants have developed poisonous chemicals which are designed to devastate enemies. |
We have only just begun to analyze and medically evaluate compounds from our rainforests systematically. Not much more than about 1 percent of the plants in the Amazon rainforests, for example, have been sampled so far. New chemicals are being discovered in their dozens but few so far have been shown to have promising medicinal properties. At the same time, of course, the rainforests of the Amazon and elsewhere are being destroyed at a rate which is greater than the pace of evaluation of the plants found there. Potential remedies for illness are likely being eliminated; we shall never know for sure. |
One of the most important, relatively recent rainforest additions to the list of medicinal plants is the Madagascar periwinkle (Catharanthus roseus), discovered in the early 1960s. More than 100 chemicals of some interest have been isolated from this plant so far. The most important, medically, are vinblastine and vincristine, both used in treatment of certain cancers. Vinblastine offers a cure rate of better than 80 percent among those struck down by Hodgkin's disease while vincristine produces a remission rate of about 90 percent among children suffering from acute and lymphatic leukemia. |
One current, intensive search is for plant products which could aid sufferers from arthritis. Millions of people around the world suffer from one or more of as many as 200 different types of this debilitating illness. More and more sufferers are seeking relief by turning to homeopathy, with some success. Reportedly, an oil extracted from the evening primrose (Oenothera species) shows promise for improving the condition of significant numbers of arthritis patients. This oil has also been used to help hyperactive children as well as sufferers from migraine, asthma, eczema, hypertension, premenstrual syndrome, Parkinson's disease, and multiple sclerosis. Evening primrose oil may be one more significant plant product in the near future in Western medicine. |
Conclusion
Only a few of the more familiar medicines isolated from plants over the centuries have been touched on here. The list is a very long one and could include other well-known substances like eucalyptus, camphor, wych hazel, liquorice, belladonna, senna, and ipecac, to mention only a few more of great value world-wide. |
It would seem that the contempt of some for plant cures in modern Western medicine is misplaced. Not only are some of the oldest of our ailment remedies still among the most popular of our curatives but we are also rediscovering in the West something fortunately not forgotten in other areas of the world; that plants can help to keep us healthy. They may, indeed, offer the only hope for the future in cases where the useful chemicals they contain are too complex or difficult to manufacture artificially. Regarding green plants as coru copiae of medicinals is more of a truth than we have recently been willing to admit. Mother Nature is, arguably, still the best chemist around! |
|
| |
