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Natural products are chemical compounds produced by organisms like animals, plants and microorganisms. They can be divided into primary and secondary metabolites. Beyond there are still more classes of natural products. Many natural products have a similar basic structure and can therefore be divided by similar chemical or biosynthetic aspects in classes of natural products.
Natural products are (often highly potent) biologically-active substances. They affect the metabolism, the central nervous system and they are component of defense mechanisms of plants and animals. They were therefore significantly important in the development of the pharmaceutical industry. Many drugs are natural products or are derived from their basic structure.
This wiki focuses on secondary natural products.
The isolation of natural products depence on the nature of the natural products. In general, the chemical compounds are separated based on the following properties:
The most common methods for natural products are the
The primary metabolites are essential for the survival of the organisms. They are formed or decomposed in the primary metabolism. The primary metabolism is directly involved in all important processes like in normal growth, development and reproduction. Parts of primary metabolism are, for example, the citric acid cycle or the photosynthesis. It thus serves to energy supply, the synthesis of important building blocks and survival of a cell. The primary metabolism is almost identical in every organism.
The resulting primary metabolites are therefore substances that are directly necessary for survival and required by all organisms. These include:
In contrast to the primary metabolism in the secondary metabolic reactions take place, which are not necessarily for the survival of the cells. The second metabolism from one organism is mostly different fprm another organism. It is variable depending on the nature of the organism's and on the specific cell of the organism. The resulting compounds are called secondary metabolites. The result is a high variability of secondary metabolities. Today about 200 000 are known. Their effect on the organism, however, are often unknown.
The following division into classes reflects the chemical characterization of the compounds (such as terpenes, steroids, coumarins), their physical characterization (essential oils) and their effect on humans (bitter compounds). This results in duplication. Many terpenes are, for example, the main constituent of an essential oil.
Essential Oils are obtained by steam distillation from plants. There, they are usually in the low single-digit percentage range available. They are complex mixtures of diverse materials. Essential oils are highly volatile and are often used in cosmetics, in the perfume industry and in the food industry because of their flavor.
To the class of alkaloids are nitrogenous secondary metabolites. Many alkaloids are polycyclic and they are highly active drugs that are effective even in small doses. Known representatives of the alkaloids are for example:
The class of the bitter compounds include the compounds that taste bitter. Thus they do not have a similiar chemical structure. They are defined according to their action. Many bitter substances simultaneously belong to other classes of compounds (eg alkaloids or glycosides).
Natural products can be stored in plants as glycosides. Coumarin is for example stored as a glycoside and enzymatically released when the cells get damaged. The characteristic smell of fresh hay comes therefore from coumarin. Glycosides consist of a sugar part (the Glycon) and a non-sugar part (the aglycone).
Polyketides are natural productes that are biosynthesized via the polyketide pathway. Their chemical structure is variable, they have no common skeleton. There are important polyketides such as the epothilones, which are important anti-cancer drugs.
Steroidsare characterized by their uniform steroid backbone. They are often of important biochemical significance. So many vitamins are steroids and some steroid hormones are active as sex hormones. The cardiac glycosides all contain a steroid backbone.
Terpenes represent the largest group of natural products, which are characterized in there isoprene units. They are biosynthesized from an activated isoprene molecule. Within the terpenes a distinction is made between mono-, di-, tri-, tetra-, sesqui-and polyterpenes.
Secondary natural products have a wide range of applications in medicine, cosmetics and food industries.
Secondary metabolites played an important role from the beginning of medical applications. In the Middle Ages the antipyretic and analgesic action of willow bark was known. This effect comes from salicin, a glycoside, which is metabolized in the body to salicylic acid. Hence the drug aspirin, which has as an active ingredient acetylsalicylic acid developed.
The medical applications are displayed at the individual substances themselves.
Before the possibility of chemical synthesis of dyes, dyeing with natural materials was the only way to dye clothes. Woad, madder dyeing & coloring chamomile were popular dye plants. It was often dyed yellow using flavonoids. However, indigo dye, an indole, was a popular blue coloring of natural products.
With the begining of the chemical industry, dyeing with natural materials until today almost disappeared.
The use as dyes are shown in the individual natural products.
A partial list of natural products that are discussed here:
The collected information are from lectures and the following sources. I would also like to incorporate current publications in the future.