Plant in medicine: the origins of pharmacognosy

Plant in medicine: the origins of pharmacognosy

The universal role of plants in the treatment of disease is exemplified by their employment in all the major systems of 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) systems centred 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 nc), 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 (first 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 BC) and Unani medicine (Kitab-Al-ShiJa, the 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 ffansmitted orally from generation to generation by 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 including 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 betteru nderstandinga nd utilization of medicinal plants. A perusal ofthe monographs on crude drugs in a modem pharmacopoeia at once illusfates the necessity for a multidisciplinary approach. Unlike those who laid the foundations of pharmacognosy, no one person can now expect to be an expert in all areas and, as is illustrated in 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 recorded by Dr K. Ganzinger (Sci. Pharm.1982, 50, 351), the terms 'pharmacognosy' and 'pharmacodynamics' were probably first coined by Johann Adam Schmidt (1759-1809) in his hand-written manuscript Lehrbuch der Materia Medica, which was posthumously published in Vienna in 1811 . Schmidt was, unril his death, professor a 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. Pharmacognosy is closely related to botany and plant chemistry and, indeed, both originated from the eartier scientific studies on 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 powde 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 techniques and pharmacologicai testing procedures means that new plant drugs usually find their way into medicine as purified substances rather than in the form of galenical preparations. Preparation is 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 procedures necessary for the identification and determination of purity of the preparation supplied. Similar remarks apply to such drugs as Rauwolfia, the modem preparations of 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 necessitatesa, as in the case of Catharanthus roseus, Coleus forskohlii, Arnica montana and Taxus brevfolia, research into the cultivation or a.rtificial propagation by cell culture, etc., of such species. In order to avert the type of supply crisis that arose at the clinical trial stage with the anticancer drug taxol, isolated from T. 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, 165'7).

However, it has been repofied that as a result of demand for the new drug galanthamine (qv) for the treatmento f Alzheimer's disease, the native source of Leucojum aestivum is now in danger.

The use of single pure compounds, including synthetic drugs, is not without its limitations, and in recent years there has been an immense revival in interest in the herbal and homoeopathic systems of medicine, both of which rely heavily on plant sources, At the 9^th Congress of the Italian Society of Pharmacognosy (1998) it was stated that the current return of phytotherapy was clearly reflected by the increased market of such products. In 1995 the latter, for

Europe, reached a figure of $6 billion, with consumption for Germany $2.5 billion, France $1.6 billion and ltaly 600 million. In the US, where the use ofherbal products has never been as strong as in continental Europe, the increase in recent years has also been unprecedented with the market for all herb salesr eaching a peak in 1998 approaching $700 million. Again, illustrating the same trend, the editor of Journal of Natural Products, 1999, writes that in response to the increasing prominence of herbal remedies, additional contributions describing scientific investigations of a rigorous nature are welcomed.

Undoubtedly, the plant kingdom still holds many species of plants containing substance of medicinal value  which have  yet to be discovered; large numbers of plants are constantly being screened for their possible pharmacological value (particularly for their anti-inflammatory, hypotensive, hypoglycaemic, amoebicidal, anti-fertility, cytotoxic, antibiotic and anti-Parkinsonismp roperties). Pharmacognosistsw ith a multidisciplinary background are able to make valuable contributions to these rapidly developing fields of study.