Plants in medicine: originsof the p

Plants in medicine: originsof the pharmacogno cy

The universal role of plants in the treatment of diseaseis exemplified by their employment in all the major systemsof medicine irrespective of the underlying philosophical premise. As examples, we have Western medicine with origins in Mesopotamia and Egypt, the Unani (Islamic) and Ayurvedic (Hindu) systemscentred in western Asia and the Indian subcontinent and those of the Orient (China, Japan,Tibet, etc.). How and when such medicinal plants were first used is, in many cases, lost in pre-history, indeed animals, other than man, appear to have their own materia medica. Following the oral transmission of medical information came the use of writing (e.g. the Egyptian Papyrus Ebers c.1600 BC), baked clay tablets (some 660 cuneiform tablets c. 650 ec from Ashurbanipal's library at Nineveh, now in the British Museum, refer to drugs well-known today), parchments and manuscript herbals, printed herbals (invention of printing l44O AD), pharmacopoeias and other works of reference (ftrst London Pharmacopoeia, 1618; first British Pharmacopoeia 1864), and most recently electronic storage of data. Similar records exist for Chinese medicinal plants (texts from the 4th century BC), Ayurvedic medicine (Ayurveda 2500-600 nc) and Unani medicine (Kitab-Al-ShiJa, rhe Magnum Opus of Avicenna,980-1037 AD).

In addition to the above recorded information there is a great wealth of knowledge concerning the medicinal, narcotic and other properties of plants that is still transmitted orally from generationto generationby tribal societies, particularly those of tropical Africa, North and South America and the Pacific countries. These are areas containing the world's greatest number of plant species, not found elsewhere, and with the westernization of so many of the peoples of these zones there is a pressing need to record local knowledge before it is lost forever. In addition, with the extermination of plant species progressing at an alarming rate in certain regions, even before plants have been botanically recorded, much less studied chemically and pharmacologically, the need arises for increased efforts directed towards the conservation of gene pools.

A complete understanding of medicinal plants involves a number of disciplines in cluding commerce, botany, horticulture, chemistry enzymology, genetics, quality control and pharmacology. Pharmacognosy is not any one of these per se but seeks to embrace them in a unified whole for the better understanding and utilization of medicinal plants. A perusal of the monographs on crude drugs in a modern pharmacopoeia at once illusfates the necessity for a multidisciplinary approach. Unlike those who laid the foundations of pharmacognosy, no one person can now expectto be an expert in all areas and, asis illustratedin the next chapter, pharmacognosy can be independently approached from a number of viewpoints.

The word 'pharmacognosy'had its debut in the early 19th century to designate the discipline related to medicinal plants; it is derived from the Greek pharmakon, 'a drug', and gignosco, 'to acquire a knowledge of' and, as recordedby Dr K. Ganzinger(Sci. Pharm.1982, 50, 351), the terms 'pharmacognosy' and 'pharmacodynamics' were probably first coined by JohannAdam Schmidt (1759-1809) in his hand-written manuscript Lehrbuch der Materia Medica, which was posthumously published in Vienna in 18I 1. Schmidt was, unril his death, professor at the medico-surgical Joseph Academy in Vienna; interestingly he was also Beethoven's physician. Shortly after the above publication, 'pharrnacognosy' appears again in 1815 in a small work by Chr. Aenotheus Seydler entitled Analecta Pharmacognostica.

Pharmacognosyis closely related to botany and plant chemistry and, indeed, both originated from the eartier scientific studieson medicinal plants. As late as the beginning of the 20th century, the subject had developed mainly on the botanical side, being concemed with the description and identification of drugs, both in the whole state and in powder and with their history, commerce, collection, preparation and storage. Such branches of pharmacognosy are still of fundamental importance, particularly for pharmacopoeial identification and quality control purposes, but rapid developments in other areas have enormously expanded the subject.

The use of modern isolation techniquesand pharmacological testing procedures means that new plant drugs usually find their way into medicine as purified substances rather than in the form of galenical preparations. Preparationis usually confined to one or a few companies who process all the raw material; thus, few pharmacists have occasion to handle dried Catharanthus roseils although they are familiar with formulations of the isolated alkaloids vinblastine and vincristine. For these new drugs it is important that the pharmacist, rather than being fully conversant with the macroscopical and histological characters of the dried plant, is able to cary out the chromatographic and other pro cedures necessary for the identification and determination of purity of the preparation supplied. Similar remarks apply to such drugs as Rauwolfia, the modern preparationsof ergot, and the cardioactive and purgative drugs.

When specific plants,including those used in traditional medicine, suddenly become of interest to the world at large, the local wild sources soon become exhausted. This necessitates, in the caseof as Catharanthus roseus, Coleus forskohlii, Arnica montana and Taxus brevfolia, research into the cultivation or artificial propagation by cell culture, etc., of such species. order to avert the type of supply In crisis that arose at the clinical trial stage with the anticancer drug taxol, isolated from 7. brevfolia, the US National Cancer Institute has initiated plans for future action when a similar situation again arises (see G. M. Cragg et al., J. Nat. Prod., 1993, 56, 1657).