Fundamentals of Biochemistry - A. A. Anisimov 1986

Protein and Amino Acid Metabolism
Alkaloids

Alkaloids are substances of plant origin that contain nitrogen as part of a ring Structure and function as organic bases. In plants, they form Water-soluble salts with organic acids.

A common property of all alkaloids is their ability to exert a potent physiological effect on the Human and Animal Organism. In small doses, most alkaloids stimulate The Nervous system, while in large doses they have a depressant effect. Many of them are powerful poisons (such as curare).

Research by A. A. Shmuk in the USSR (1948) and K. Mothes in the GDR (1969) demonstrated that alkaloids undergo active enzymatic transformations during plant life processes and are not metabolically inert, as was previously assumed. They appear to serve as an intermediate form in The conversion of nitrogenous compounds within plants, wherein nitrogenous metabolic products are detoxified and stored. The Role of certain tobacco alkaloids (such as nicotine) as starting Materials for the synthesis of pyridine dehydrogenases has been established. Experimental evidence also indicates the potential involvement of alkaloids in plant redox reactions. Amino Acids (Tyrosine, Tryptophan, etc.) serve as precursors for the synthesis of many alkaloids.

Alkaloids vary widely in structure and are classified into groups based on the Chemical Nature of their nitrogenous heterocycle.

The most prominent representative of the quinoline derivative group is quinine. It is found in the bark of the cinchona tree and is used in medicine to treat malaria.

Morphine and codeine, Representatives of the isoquinoline alkaloid group, are found in opium, the milky juice of the opium poppy. Strychnine, found in the seeds of the nux vomica tree, belongs to the group of indole-derived alkaloids. Large doses of strychnine induce severe convulsions and death from respiratory paralysis.

One of the representatives of the tropane alkaloid group is atropine, found in plants of The Nightshade family: deadly nightshade, henbane, and various species of thornapple. It is widely used in medicine. Atropine causes significant pupil dilation, which is utilized in fundus examinations. In therapeutic doses, it stimulates Respiration and increases Heart rate.

The nicotine molecule consists of linked pyridine and pyrrolidine rings. Nicotine is a colorless, oily liquid that affects both the central and peripheral nervous systems. Poisoning by it leads to death from respiratory paralysis.

Recently, evidence has emerged regarding the presence of alkaloids in animals as well, such as in the Skin secretions of certain poison dart frogs.