This book has been written primarily for pharmacy undergraduates to provide a modern text to complement lecture courses dealing with pharmacognosy and the use of natural products in medicine. Nevertheless, it should be of value in most other courses where the study of natural products is included, although the examples chosen are predominantly those possessing pharmacological activity.
For centuries, drugs were entirely of natural origin and composed of herbs, animal products, and inorganic materials. Early remedies may have combined these ingredients with witchcraft, mysticism, astrology, or religion, but it is certain that those treatments that were effective were subsequently recorded and documented, leading to the early Herbals. The science of pharmacognosy - the knowledge of drugs - grew from these records to provide a disciplined, scientific description of natural materials used in medicine. Herbs formed the bulk of these remedies. As chemical techniques improved, the active constituents were isolated from plants, were structurally characterized, and, in due course, many were synthesized in the laboratory. Sometimes, more active, better tolerated drugs were produced by chemical modifications (semi-synthesis), or by total synthesis of analogues of the active principles.
Gradually synthetic compounds superseded many of the old plant drugs, though certain plant-
derived agents were never surpassed and remain as valued medicines to this day. Natural drugs derived from microorganisms have a much shorter history, and their major impact on medicine goes back only about 60 years to the introduction of the antibiotic penicillin. Microbially produced antibiotics now account for a very high proportion of the drugs commonly prescribed. There is currently a renewed interest in pharmacologically active natural products, be they from plants, microorganisms, or animals, in the continued search for new drugs, particularly for disease states where our present range of drugs is less effective than we would wish. Herbal remedies are also enjoying a revival as many sufferers turn away from modern drugs and embrace 'complementary medicine'.
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