Chapter 2 The scope and practice of pharmacognosy
Until relatively recently pharmacognosy was regarded, almost exclusively, as a subject in the pharmaceutical curriculum focused on those natural products employed in the allopathic system of medicine. Coincident with the increasing attractiveness of alternative (complementary) therapies and the tremendous range of herbal products now generally available to the public, regulatory requirements covering medicinal herbs have been put in place by many countries in order to control the quality of these products. Monographs are now available on a large number of such drugs giving descriptions, tests for identity and purity and assays of active constituents. These monographs are being compiled by a number of bodies (see below). In this respect recognition should be given to the pioneering production of the British Herbal Pharmacopoeia, first produced in 1974 with the latest volume in 1996. Pharmacognosy is also important in those countries having their own systems of medicine in which plants are important components.
Many crude drugs once generally categorized as herbal remedies are now, in accordance with Continental European practice, described in the British Pharmacopoeia (BP). Chromatographic, chemical and physical tests, together with assay procedures, are given for many drugs for which previously there was no quantitative evaluation of the chemical constituents available. The importance of quality control is paramount, as the demand and the possibility of substitution has increased. The upsurge in the marketing of Chinese and Asian traditional medicines worldwide, for which there is a need for adequate control, adds a further dimension to pharmacognosy; pharmacopoeial monographs now include Liquorice for use in Chinese medicine, Chinese angelica root and Astragalus root. It is understood that further monographs on Chinese and Indian drugs for use in traditional medicine are to be included in the BP 2009.
Although pharmacognosy is principally concerned with plant materials, there are a small number of animal products which are traditionally encompassed within the subject; these include such items as beeswax, gelatin, woolfat, vitamins, etc. Other natural products such as the antibiotics, hormones and others may or may not be involved, depending on the teaching practice of a particular institution. Marine organisms, both plant and animal, with potent pharmacological actions are receiving increasing attention in the search for new drugs. Materials having no pharmacological action which are of interest to pharmacognosists are natural fibres, flavouring and suspending agents, colourants, disintegrants, stabilizers and filtering and support media. Other areas that have natural associations with the subject are poisonous and hallucinogenic plants, allergens, herbicides, insecticides and molluscicides.
Vegetable drugs can be arranged for study under the following headings.
The following list of works, arranged in the above five groups, will serve as examples and also provide a useful list of textbooks and works of reference; those no longer in print may be found in established pharmaceutical libraries.
Barnes J, Anderson LA, Phillipson JD. Herbal medicines, 3rd edn. London: Pharmaceutical Press, 2007.
Bisset NG, Wichtl M, editors. Herbal drugs, a handbook for practice on a scientific basis. Stuttgart: Medpharm Scientific Publishers, 1996.
Bradley PR. 2006 British herbal compendium. Vols I, II. British Herbal Medicine Association. Bournemouth, UK, 1992.
British Pharmacopoeia and preceding edns, 2008.
British Herbal Pharmacopoeia. British Herbal Medicine Association. Exeter, UK, 1996.
Duke JA. Handbook of medicinal herbs, 2nd edn. New York: CRC Press, 2002.
Martindale: the Complete Drug Reference. 35th edn. Pharmaceutical Press, London, 2007.
United States Pharmacopoeia 29/National Formulary 24 and Supplement, 2006.
Williamson EM. Potter’s herbal cyclopaedia. Saffron Walden: CW Daniel Co, 2002.
The national pharmacopoeias of many countries and the European Pharmacopoeia; the relevant crude drug monographs of the latter are included in the British Pharmacopoeia
Paris RR, Moyse H. 1967, 1971 Matière médicale. 3 vols. Masson, Paris, 1965.
Thoms H. Handbuch der Pharmacie. Pharmacognosy. 2 vols. Urban and Schwarzenberg, Berlin, Band V, 1929.
Trease GE, Evans WC. Pharmacognosy, 10th edn. London: Baillière Tindall and Cassell, 1972.
Berger Berger F Handbuch der Drogenkunde. Maudrich, Vienna, Vol I, Barks and flowers, 1949; Vol II, Leaves, 1950; Vol III, Fruits and woods, 1952; Vol IV, Herbs, 1954; Vol V, Roots, 1960; Vol VI, Resins etc and seeds, 1964; Vol VII, Index, 1967
Jackson BP, Snowdon DW. Atlas of microscopy of medicinal plants, culinary herbs and spices. London: Belhaven Press, 1990.
Wallis TE. Textbook of pharmacognosy, 5th edn. London: Churchill Livingstone, 1967.
4. Pharmacological or Therapeutic
Der Marderosian A, Liberti LE. Natural product medicine. Philadelphia, PA, USA: GF Stickley, 1988.
Heinrich M, Barnes J, Gibbons S, Williamson EM. Pharmacognosy and phytotherapy. Edinburgh: Churchill Livingstone, 2004.
Pratt R, Youngken HWJr. Pharmacognosy, 2nd edn. Philadelphia, PA, USA: Lippincott, 1956.
Ross MSF, Brain KR. An introduction to phytopharmacy. Tunbridge Wells: Pitman Medical, 1977.
Bruneton J. Pharmacognosy, phytochemistry, medicinal plants. Intercept Scientific, Medical and Technical Publications, 1999.
Dewick PM. Medicinal natural products, a biosynthetic approach, 2nd edn. Chichester: John Wiley, 2002.
Hänsel R, Sticher O, Steinegger E. Pharmakognosie-Phytopharmazie, 6th edn. Berlin: Springer, 1999. (in German)
Robbers JE, Speedie MK, Tyler VE. Pharmacognosy and pharmacobiotechnology. Baltimore: Williams & Wilkins, 1996.
Tschirch Tschirch A Handbuch der Pharmakognosie. Tauchnitz, Leipzig (two editions and numerous volumes up to 1933)
With the increase in interest in medicinal plants world-wide there are now many publications covering regional areas of the globe. Treatment of the plants in these works may be on any of the above lines. Some examples are given following the Introduction to Part VI.
As mentioned previously, a number of bodies have implemented research and published monographs on medicinal herbs. The aim has been to set standards for quality, efficacy and safety in order that the many traditional herbs meet legal requirements. The following are of note:
These were developed for the German Federal Health Authority between 1978–1994 and involve 324 herbs used in German traditional medicine. The monographs give sources, constituents and considerable pharmacological and clinical information. They have now been translated into English and published by the American Botanical Council in 1999 as a single work followed by expanded monographs in 2000.
ESCOP (European Scientific Cooperative for Phytotherapy) is an affiliation of European associations which has produced 60 monographs on herbal drugs, published in loose-leaf form in six fascicules, harmonizing the standards for these drugs throughout the European Union. Information is given on approved therapeutic uses, and unlike the Commission E monographs, provides references. The second edition of ESCOP Monographs was published in 2003, and a third edition is in the course of preparation.
The American Herbal Pharmacopoeia (1997–2005) has monographs on a selection of traditional indigenous herbs with some overlap with the European monographs. Treatment of individual drugs can be extensive, for example, the St John’s wort monograph published in HerbalGram 1997, No 4 extends to 32 pages with over 150 references, colour photographs and chemical formulae.
The World Health Organization published Volume 1 of its Monographs on Selected Medicinal Plants in 1999. It contains standards for quality of drugs together with a therapeutic section; 31 plant species, the majority of which are also included in the above lists, are considered. Volume 2 was published in 2002.
The United States Pharmacopoeia is also producing herbal monographs. Eleven have been published, all involving drugs treated above, and twelve more were expected during 2000.
Students wishing to read original research will find many references in this book and should learn how to find similar ones for themselves. As no one can hope to read all the scientific literature that is published, special journals are devoted to the publication of brief abstracts from the original papers. Such abstracts give the author’s name, the subject of the research, the reference necessary to locate the paper in the original journal and usually a brief outline of the work it contains. Most pharmacy department libraries contain Chemical Abstracts and Biological Abstracts, which in the appropriate sections cover all areas of pharmacognosy. Even so, the systematic searching of the abstracts to cover a broad field of interests can itself be most time-consuming, and publications such as Chemical Titles and Current Contents can be used to give a more rapid indication of recent publications. Phytotherapy Research regularly includes a selected bibliography relating to plant drugs. Information storage and retrieval is now itself a science, and a glance at the shelf-space occupied by succeeding years of Chemical Abstracts is sufficient to indicate that before long, if not already, manual searches of the literature will become impossibly long procedures. In many libraries, hard copies of these publications and of the journals mentioned below are no longer available, but they can be accessed on-line. Inevitably it will be necessary to rely on databases for literature scanning. Pharmacognosy Titles is a computer abstract coverage of phytochemical research publications up to 1974 (10 vols) produced under the direction of Professor N. Farnsworth, University of Illinois. Subsequently, Farnsworth introduced NAPRALERT, a Natural Product Database which is mainly, but not entirely, post-1975 and is viewed by many as a logical and indispensable collection of pharmacognostic information. The NAPRALERT database is available on a scheduled-fee basis to scientists, industrial firms, government agencies and academic institutions. Among other useful databases having a relevance to pharmacognosy and published on the Web are MEDLINE, compiled by the US National Library of Medicine and EMBASE, produced by Excerpta Medica.
Some journals—for example, Planta Medica, Journal of Ethnopharmacology, Phytochemistry and Journal of Natural Products—periodically contain reviews on some aspect of medicinal plants. Other journals containing research papers of pharmacognostical interest are Natural Product Research and Natural Product Sciences. Periodical publications appearing in bound form and devoted to reviews on certain aspects of plant constituents are useful for updating; often the reviews cover only the advances in a particular field since the previous volume. Examples are Natural Product Reports (six issues per year) and Alkaloids (Academic Press).
A series of multi-author books Medicinal and Aromatic Plants – Industrial Profiles (R. Hardman, series editor, CRC Press, Boca Raton, FL) provides an in-depth coverage of major medicinal and aromatic plants for specific genera; to date (2007) forty-five volumes have been published. Individual books for appropriate drugs are cited in Part 5 under ‘Further reading’. Books that are not part of a series but, like the above, multi-author and dealing with certain specialized areas (e.g. alkaloids, flavonoids, isoprenoids), continually appear and generally give up-to-date information (in so far as any book can). Symposia which cover various aspects of pharmacognosy are frequently held in various parts of the world and scientists can easily become acquainted with others having like interests. Often the informal discussions which invariably arise at such meetings can be an extremely useful means of disseminating information. In addition, the lectures presented at such meetings are often subsequently published in book form. Modern communication systems make world-wide contact between researchers much simpler.
Now available to Western scientists interested in oriental medicine is the quarterly journal Abstracts of Chinese Medicine, published by the Chinese University of Hong Kong. This gives abstracts in English of significant Chinese research papers from more than one hundred scientific journals not readily available outside China.
Useful dictionaries to be found in most University libraries include Dictionary of Organic Compounds consisting of 7 volumes and 10 supplements (to 1992), Dictionary of Alkaloids (2 volumes) (1989), Dictionary of Terpenoids (1991) and Dictionary of Natural Products (1994) all published by Chapman and Hall and also Phytochemical Dictionary: A Handbook of Bioactive Compounds from Plants (1993), published by Taylor and Francis. Some of these more expensive volumes are available on CD-ROM.