Biologically active principles, chemical

Advances in research are performed on the genus Astragalus and about 100 different species have been chemically studied imtill now [249]. The genus appears highly uniform from a chemical point of view, with three kinds of biologically active principles and three diffent groups of toxic compounds. The active constituents are saponins, flavonoids, and polysaccharides, while nitro-compoimds, indolizidine alkaloids and the seleniferous derivatives are included in the poisonous groups. 

Buuc r. R. Echinacea Biological effects and active principles. In Law son, L. D..and Bauer. R. (eds.). Phytomedicincs of Europe Chemistry and Biological Activity. American Chemical. Society Symposium Series. New Y(Kk. Oxford University Pre.s.s. 1998. p. 140. 

If an interesting activity is described, larger quantities (10-100 kg) of the plant material are collected, from which chemists purify and characterize the active principle. The active principle is known as a lead compound . Chemists will then usually attempt to modify the lead compound in order to render it more therapeutically useful (e.g. make it more potent, or perhaps increase its hydrophobicity so that it can pass through biological membranes). This is then subjected to further pre-clinical trials, and chemists determine whether an economically feasible method, allowing the drug s chemical synthesis, can be developed. 

At the turn of the nineteenth century, methods became available for the isolation of active principles from crude drugs. The development of chemistry made it possible to isolate and synthesize chemically pure compounds that would give reproducible biological results. In 1806, Serturner (1783-1841) isolated the first pure active principle when he purified morphine from the opium poppy. Many other chemically pure active compounds were soon obtained from crude drug preparations, including emetine by Pelletier (1788-1844) from ipecacuanha root quinine by Carentou (1795-1877) from cinchona bark strychnine by Magendie (1783-1855) from nux vomica and, in 1856, cocaine by Wohler (1800-1882) from coca. 

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