Drug Sources

Drug and Active PrincipleUntil the end of the 19th century, medicines were natural organic or inorganic products, mostly dried, but also fresh,plants or plant parts. These might contain substances possessing healing (therapeutic) properties or substancesexerting a toxic effect.In order to secure a supply of medically useful products not merely at thetime of harvest but yearround, plantswere preserved by drying or soaking them in vegetable oils or alcohol. Dryingthe plant or a vegetable or animal product yielded a drug (from French“drogue” – dried herb). Colloquially, thisterm nowadays often refers to chemicalsubstances with high potential for physical dependence and abuse. Used scientifically, this term implies nothing aboutthe quality of action, if any. In its original, wider sense, drug could refer equally well to the dried leaves of peppermint, dried lime blossoms, dried flowersand leaves of the female cannabis plant(hashish, marijuana), or the dried milkyexudate obtained by slashing the unripeseed capsules of Papaver somniferum(raw opium). Nowadays, the term is applied quite generally to a chemical substance that is used for pharmacotherapy.

Soaking plants parts in alcohol(ethanol) creates a tincture. In this process, pharmacologically active constituents of the plant are extracted by the alcohol. Tinctures do not contain the complete spectrum of substances that existin the plant or crude drug, only thosethat are soluble in alcohol. In the case ofopium tincture, these ingredients arealkaloids (i.e., basic substances of plantorigin) including: morphine, codeine,narcotine = noscapine, papaverine, narceine, and others.Using a natural product or extractto treat a disease thus usually entails the administration of a number of substances possibly possessing very different activities. Moreover, the dose of an individual constituent contained within agiven amount of the natural product issubject to large variations, depending  upon the product‘s geographical origin (biotope), time of harvesting, or condi tions and length of storage. For the same reasons, the relative proportion of indi vidual constituents may vary considerably. Starting with the extraction of morphine from opiumin 1804 by F. W. Sertürner (1783–1841), the active principles of many other natural products were subsequently isolated in chemi cally pure form by pharmaceutical la boratories. The aims of isolating active principles are: 1. Identification of the active ingredient(s). 2. Analysis of the biological effects (pharmacodynamics) of individual in gredients and of their fate in the body (pharmacokinetics). 3. Ensuring a precise and constant dosage in the therapeutic use of chemically pure constituents. 4. The possibility of chemical synthesis, which would afford independence from limited natural supplies and create con ditions for the analysis of structureactivity relationships. Finally, derivatives of the original constituent may be synthesized in an effort to optimize pharmacological properties. Thus, derivatives of the original constituent with improved therapeutic useful ness may be developed.