"Pharmacognosy" By Roger M. Rutz
By Roger M. Rutz
From the beginnings of Western Medicine up to the nineteenth century, the physician diagnosed the illness and prescribed a medicinal substance to treat it, while the pharmacist or apothecary collected, prepared and compounded the medicinal substance. These medicinal materials were natural products of plant, animal or mineral origin and collectively were known as “materia medica,” or medicinal materials.
The term “pharmacognosy” was introduced by C. A. Seydler, a medical student in Halle an der Saale, Prussia, in 1815. It is derived from the Greek words pharmakon, drug and gnosis, knowledge. Literally it means “knowledge of pharmaceuticals,” and it implied a knowledge of the history, distribution, cultivation, collection, selection, preparation, commerce, identification, evaluation, preservation and use of drugs and economic substances that affect the health of humans and animals. It was closely allied to and often indistinguishable from economic botany.
Today, pharmacognosy lies between the sciences of pharmacology and medicinal chemistry on the one hand and pharmaceutics and clinical pharmacy on the other hand. Pharmacology is concerned with drug actions in the body and their effects, while medicinal chemistry is the chemistry of designing synthetic drugs to have specific drug actions. Pharmaceutics involves the physical manufacturing of drugs and their delivery method to the therapeutic site in the body, while clinical pharmacy is concerned with how drugs are dispensed in a healthcare setting.
Pharmacognosy has now evolved into a science specializing in the extraction, separation, isolation and identification of the secondary metabolites of plant and animal drugs. Chemical solvents of varying polarities including water, methanol, petroleum ether and chloroform are used to make extracts from a crude drug. These extracts are then fractionated using some form of chromatography, either thin layer chromatography (TLC), gas chromatography, high performance liquid chromatography (HPLC), or column chromatography using silica gel in order to separate the compounds making up the extract. Each fraction is also screened for biological activity to guide the fractionation towards compounds that have pharmacological interest. Bioassays may include tests to determine cytotoxic, antiviral, antimicrobial, antifungal, antitumor, and mutagenic activity. Finally, upon arrival at a single, biologically active compound, the structure will be determined through mass spectrometry, nuclear magnetic resonance (NMR) (think MRI!), and x-ray crystallography. Finally, to prove the structure chemical synthesis of the compound will be performed.
Examples of the types of secondary metabolites that fall under the scope of pharmacognosy include carbohydrates; glycosides; lipids including fixed oils, fats, and waxes; essential oils; resins including oleoresins, oleogum resins, and balsams; steroids; alkaloids; peptide hormones; enzymes; vitamins; antibiotics; immunizing biologics; allergens and allergenic extracts. Pharmacognosy also interests itself with the study of poisonous plants, herbs used in the health food industry, flavoring agents and condiments in general.
Major research in pharmacognosy today is now taking place only in Germany, Japan and the People’s Republic of China.
Sciences that are related to or have a direct bearing on pharmacognosy include the following:
Biochemistry: the study of the primary metabolites produced by living organisms, which they depend on for life.
Chemotaxonomy: the taxonomic classification of plants based on the secondary metabolites they produce in common.
Economic Botany: the study of commerce involving natural products.
Ethnobotany: the study of the usage of plants among different ethnic groups.
Ethnomedicine: the study of the practice of medicine among different ethnic groups.
Ethnopharmacology: the study of plants, animals or minerals used as drugs among different ethnic groups.
Ethnotaxonomy: the study of how organisms are classified by different ethnic groups.
Marine Pharmacology: the study of marine organisms used as drugs.
Medical Botany: the study of plants used as drugs.
Natural Products Chemistry: chemistry involved with the synthesis of naturally occurring compounds.
Phytochemistry: chemistry involved with the secondary metabolites found in plants and how they are biosynthesized.
Taxonomy: the taxonomic classification and organization of living organisms.
Brady, L., Robbers, J., and Tyler, V. (1988). Pharmacognosy, 9th ed. Philadelphia, Pennsylvania: Lea & Febiger.