Alkaloids
Mostly derived from plants and other natural sources( animal ,marine) they are of basic character, having 1 or more N atoms (alkali-like) (usually in the heterocyclic ring;
They have important physiological effects in mammals and other organisms.
In most human history, plant alkaloids extracts were used as content. potions (liquid medicine) and poisons.Ancient people used plant extractscontaining alkaloids for a great treat number of diseases including: snake bite, fever and madness. Alkaloids have been used by humans for about 3000 years.( the latex of Opium Poppy (Papaver) was already used at 1200 B.C.) Coniine caused the death of Socrates. It is also recorded that Cleopatra uses atropine for her eyes.
Alkaloids are mostly found in plants and are particularly common in some families of
flowering plants. In total, more than 3,000 different types of alkaloids have been identified in more than 4,000 plant species. In general, a particular species contains only a few kinds of alkaloids, but both opium poppy (Papaver somniferum) and ergot mushroom (Claviceps) each contain about 30 different species. Some plant families are particularly rich in alkaloids;
All plants of the poppy family (Papaveraceae) are thought to contain them, for example.
Ranunculaceae (buttercups), Solanaceae (night shadows) and Amaryllidaceae (amaryllis) are other important alkaloid-containing families. Several alkaloids have been found in animal species such as New World beaver (Castor canadensis) and poison dart frogs (Phyllobates).
Ergot and a few other mushrooms produce them.
The term “alkaloid” was introduced by German pharmacist Wilhelm Meissner,and the traditional definitions of alkaloids emphasized bitter tastes, alkalinity, plant origins and physiological effects. The presence of at least one nitrogen atom is a general chemical property of alkaloid.
Alkaloids may present in various plant organs Examples:
Seeds Nux-vomica
Leaves Datura Roots Rauwolfia Barks Cinchona Stems Ephedra Latex Opium
Alkaloids play the following functions in plants:
1 -Protects plants against insects 2- As end products of metabolism 4- Energy source and nitrogen reserve 5-Toxic to insects
6- Feed deterrents(Nicotine one of the first insecticides)
Alkaloids finish with the suffix-ine, their names may be derived from Genus name e.g., Atropine from Atropa.
Species name e.g., Cocaine from Coca.
Common name e.g., Ergotamine from Ergot.
Physiological activity e.g., Emetine (emetic).
Discoverer e.g., Pelletierine from Pelletier.
Alkaloid Biosynthesis
The alkaloids are biosynthesized by complex pathways that may contain 20 or more enzymatic steps. Alkaloids in most cases are formed from L- amino acids, Tryptophan, tyrosine, phenylalanine, lysine and arginine as precursors.
Many alkaloids have significant biological activities that are usually associated with amine functions.
Several alkaloids are used medically or supply precursor structures for new synthetic drugs.
Plant tissue cultures may be an alternative method for species that are slow growing or have a small amount of active compoun/s. For this reason, biosynthetic studies can be used for commercial production of alkaloids having economic value.
In plants, alkaloids may exist in the form of organic acid salts, malate, acetate and citrate, or may be combined with other molecules such as tannins.
Opium alkaloids occur with meconic acid Cinchona alkaloids with cinchotannic acid.
Some occur in combination with sugars as glycosides e.g. Solanine
Most alkaloids show basic properties and have a lipophilic character that is soluble in apolar organic solvents and alcohol.
Several alkaloids are known for their biological properties, which can be marked as apparent toxicity or strong pharmacological capacity. The class of alkaloids has a long history of use, both legal and illegal, as drugs, stimulants and narcotic substances.
Typical alkaloids are derived from plant sources, they are basic, they contain one or more nitrogen atoms (usually in a heterocyclic ring) and they usually have biological action on man or other animals. The name ‘proto-alkaloid’ or ‘amino-alkaloid’ is sometimes applied to compounds such as hordenine, ephedrine and colchicine which lack one or more of the properties of typical alkaloids.
They may be present in the plant in free form, as salts or as N-oxides. Knowledge of the solubility of alkaloids and their salts is of pharmaceutical importance.N-oxidation products of alkaloids, especially N-oxides of tertiary alkaloids, are well-known laboratory products, The N-oxidation products of alkaloids, especially the N-oxides of tertiary alkaloids, are well-known laboratory products,
Easily prepared from the original base. Early 1920s comprehensive pharmacological and toxicological comparisons had been made of common alkaloids such as morphine, strychnine and hyoscyamine and the corresponding N-oxides. N-oxides have been found to exhibit low toxicities and low addiction compared to their corresponding tertiary alkaloids. N-oxides also show high polarity and are water soluble.
