Introduction to Pharmacognosy

Pharmacognosy is the basis of the modern sciences of drug discovery and pharmacology. It is the derivation of medicines from natural products. The word literally means "knowledge of drugs" (pharmakon = drug, gnosis = knowledge). Although pharmacognosy may be associated with the work of witch doctors, sorcerers and medicine men, it remains an important aspect of current efforts to find new and better drugs for human medical use.

History

• Human use of natural products including plants, fungi, and even animals for medicinal use is older than recorded history. Indeed, natural products were the only means of providing treatments before the advent of the scientific method and organized medicine. The benefits of certain plants or other materials were worked out by trial and error, and the knowledge passed down from one generation to the next.

  The well-known Greek and Roman philosophers of ancient times made their contributions, along with the anonymous writers of Babylonian and Egyptian texts. The term "pharmacognosy" was first used by C.A. Seydler in his thesis of 1815. A good current definition is the applied science of the biological, biochemical and economic aspects of natural drugs and their constituents.

  Pharmacognosy encompasses not only the study of the natural source material for drugs, but also their isolated chemical components and those compounds that go on to be completely synthesized in the laboratory.

Drug Discovery

• Drug discovery begins by selecting material to be screened for medicinal properties. Natural products remain important sources of test material. Although many substances have been tested for medicinal use, more remain. In addition, the way a sample is prepared or extracted can be varied in so many ways that the choices and combinations are nearly endless.

  If one particular plant is found to possess compounds of interest, related plants or plants found in the same geographic region become good candidates for screening. Promising compounds identified in initial screenings can be chemically modified in myriad ways to check for improved activity or reduced side effects. Today, drug companies use high throughput screening systems that can screen millions of test materials in just a few days.

Medicinal Plants

• Plants are the oldest source of natural drug products. Plants are large organisms that are easy to find (compared with fungi and bacteria). Early experiments with plants were sometimes based on the shape of the plant; for example, a plant part that looked like a liver was tried to treat liver disease.

  Over time, a body of knowledge emerged that included plants that have beneficial uses in the treatment of wounds or illness or for use as stimulants. Some plants, such as members of the dogbane family, have hallucinogenic properties.

  Some well-known drugs of plant origin are ephedrine, caffeine, morphine and camphor. These compounds have an affect if used in their natural or crude forms as teas, poultices or tinctures. However, their efficacy is greatly increased by isolation or synthesis of the pure active compounds.

Medicinal Fungi

• Fungi are second only to plants in their usefulness as medicinals. Through trial and error, the macrofungi (mushrooms) were eventually sorted into edible and poisonous species. Others have psychoactive properties and have been adopted for ritual or spiritual, as well as medicinal, use.

  Medicine men in one South American culture squeeze liquid from a specific mushroom into ears to treat earaches, and scientific studies have supported its efficacy. Chinese herbals contain many instances of mushroom use, which has lead to active research to isolate drug candidates from the mushrooms.

  Molds produce many antibacterial compounds, one of which---penicillin---was discovered completely by accident by Alexander Fleming.

Animal Products

• Animals are also a source of useful natural medicinal products. One well-known example is the poison from the skin of frogs (which shows promise as an analgesic and muscle relaxant). Hoofs, skin, horns and bone from animals have long been a part of traditional Chinese medicine.

  Animal products are less well-studied than plant products. Medicinal properties have be ascribed to many animals, including rhinoceroses and tigers, which are endangered, making their modern use problematic.