Arzneipflanzen – – Gestern, Heute und Morgen¹

Abstract

In the present essay medical intervention is interpreted in a very large sense. It is assumed to include prevention, diagnosis and therapy of diseases by physicians as well as revalidation and nursing of patients and all activities concerned with preparation and delivery of medicaments. Like–wise drugs (= pharmaca) are defined very loosely as preparations and articles able to prevent, cure and (or) alleviate illness. In my definition lemon juice was formerly a pharmacon used in the British navy to prevent scurvy.

The use of plants to prevent and cure disease goes far back in history of man. In antiquity spices and cosmetics (fig. 1–3) contributed to disease prevention and medicinal and toxic plants were carefully observed and described. The treatise „de Materia Medica” of Dios–curides had a long impact on medicinal thinking in Europe. It became the manual of early medieval medicine, especially North of the Alps where learned men were more dogma– and doctrine–minded than inclined to observe nature carefully and to perform experiments. Nevertheless, with Hildegard von Bingen (12th century) the study of medicinal and useful plants revived slowly and culminated in the herbals of the 16th century (e.g. Brunfels, Bock, Fuchs). Subsequently scientific botany began to evolve with scientists like Caspar Bauhin (17th century; fig. 4), Carl Linné (18th century; fig. 5) and A. P. de Candolle (19th century; fig. 6). Beginning with the 19th century medical botany or pharmacognosy diverges from pure botany and specializes in the all–round study of medicinal plants and crude drugs (e.g. Guibourt, Pereira, Hanbury, Flückiger).

In this essay in the past is intended to cover roughly the space of time between 1800–1900, today the period from 1900 until 1978 and tomorrow is reserved for some strictly personal views concerning future tasks of medicinal plant research.

IN THE PAST – A. P. de Candolle (fig. 6) initiated and stimulated phytochemical and pharmacological research with medicinal plants because he was extremely interested in the use of chemical characters in plant taxonomy. The rapid development of phytochemistry is illustrated by poppy, cinchona and coca alkaloids (fig. 7). To illustrate the rapid progress of the, whole field of pharmacognosy during the 19th century I chose the history of cinchona and coca culture in the Old World. Shortly after its isolation from cinchona bark quinine became the first highly active chemotherapeuticum and cocaine opened the field of local anaesthesia. In 1855 the Dutch established the first cinchona plantation on Java. Within 40 years they succeeded by means of botanical and agricultural research and a very rigid chemical selection to produce large amounts of high–quinine barks (fig. 8–11). Cinchona ledgeriana (fig. 9 and 11) was a key element of this success. The story of coca leaves (Erythroxylum coca) is similar. In this instance, however, the structure elucidation and synthesis of cocaine proved to be possible already in 1888. Shortly afterwards the first synthetic local anaesthetics began to compete with natural cocaine which, as a matter of fact, was prepared by partial synthesis from ecgonine, benzoic acid and methanol in these days. Orthoform (1897), anaesthesin (1902) and novocaine (1905) belong to the first synthetic drugs used in medicine.

TODAY – The redetection of Gregor Mendel's laws of heredity by Correns, von Tschermak and de Vries and the rapid start of genetics as a science opened many new possibilities for plant breeding. On the basis of the knowledge of genetic variation within populations and of the segregation and recombination of genes in populations of sexual organisms rapid progress – among other types of breeding – in chemical plant breeding (comparable to the cinchona work, but now understandable in terms of genes and gene exchanges and interactions) became possible.

The rubber tree, Hevea brasiliensis, is used here to demonstrate a few aspects of this new area of biological knowledge. Caoutchouc is considered to be a pharmacon because it is used for the preparation of elastic adhesives and plasters and for the fabrication of many and diverse utensils important to modern medicine. The larger amount of rubber, of course, is used for technical purposes. Two years ago the centenary of domestication of the rubber tree was celebrated with a symposium in Sri Lanka (formerly Ceylon). All Hevea-plantations derive ultimately from 26 trees transported in 1876 as seedlings from Kew to the Royal Botanical Garden of Ceylon. Therefore the gene pool on which Old World plantations are based is rather limited. Future tasks comprise among other activities a thorough exploration of the comparium to which Hevea brasiliensis belongs. The amelioration of rubber production depends largely on the collection, preservation and careful investigation of new genotypes, ecodemes and Hevea species crossable with Hevea brasiliensis.

TOMORROW – It should generally be accepted that the conservation of gene pools of medicinal plants is urgently needed. Each ecodeme and each taxon which are extirpated by the activities of man will no longer be available for research and therapy in future generations.

Moreover, an inventory should be made of all the knowledge acquired empirically by man during many centuries; ethnobotany should register local knowledge about plants before it is lost for ever. It is stressed that this presently fashionable field of investigation deserves due attention and financial support but that it is by no means new. Many botanical explorers of the past century contributed to it. As far as medicinal plants are concerned, scientists like Flückiger, Dragendorff, Zornig, Tschirch and Hartwich initiated and developed ethnobotanical research. Overlooking predecessors is not the way to perform a scientific job as best it can be done. Unfortunately many of the modern ethnobotanists ignore their predecessors.

A well balanced scientific knowledge of the medicinal properties of plant species and of the crude drugs and galenical preparations derived from them requires intensivation of clinical pharmacological research and an adequate development of the pharmacology of complex mixtures like plants, crude drugs and extractives. The fashionable pharmacology of pure – mostly synthetic – compounds is not adequate to a satisfactory evaluation of medicinal plants. If medicine really continues to consider solus aegroti summa lex as the basic principle of its attitude, it should heavily claim and ardently support efforts to, and at the same time create new possibilities for a truely scientific evalution of all medicinal plants. They represented, in fact, the majority of medicaments available to man before 1900. These are by no means new thoughts as illustrated by a sentence (see p. 23) written by Hugo Schulz (fig. 12) in 1919.

Key Word Index

Medicinal Plants - Medical Botany - Spices and Cosmetics in Antiquity - Pharmacognosy - History of Cinchona Bark and Quinine Production - History of Coca Leaf and Cocaine Production - History of the Rubber Tree and of Caoutchouc Production - Cinchona ledgeriana - Erythroxylum coca - Hevea brasiliensis - Conservation of Gene Pools of Medicinal Plants - Ethnobotany - Folk Medicine - Clinical Pharmacology - Pharmacology of Crude Drugs